diff --git a/Cargo.lock b/Cargo.lock
index c2ea9a9..5a94fa6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -67,9 +67,11 @@ name = "aoc23"
 version = "0.1.0"
 dependencies = [
  "async-recursion",
+ "derive_builder",
  "expanduser",
  "futures",
  "itertools",
+ "rayon",
  "regex",
  "reqwest",
  "reqwest-middleware",
@@ -114,7 +116,7 @@ checksum = "5fd55a5ba1179988837d24ab4c7cc8ed6efdeff578ede0416b4225a5fca35bd0"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.39",
 ]
 
 [[package]]
@@ -125,7 +127,7 @@ checksum = "a66537f1bb974b254c98ed142ff995236e81b9d0fe4db0575f46612cb15eb0f9"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.39",
 ]
 
 [[package]]
@@ -329,6 +331,30 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "crossbeam-deque"
+version = "0.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ce6fd6f855243022dcecf8702fef0c297d4338e226845fe067f6341ad9fa0cef"
+dependencies = [
+ "cfg-if",
+ "crossbeam-epoch",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-epoch"
+version = "0.9.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ae211234986c545741a7dc064309f67ee1e5ad243d0e48335adc0484d960bcc7"
+dependencies = [
+ "autocfg",
+ "cfg-if",
+ "crossbeam-utils",
+ "memoffset",
+ "scopeguard",
+]
+
 [[package]]
 name = "crossbeam-utils"
 version = "0.8.16"
@@ -338,6 +364,41 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "darling"
+version = "0.14.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b750cb3417fd1b327431a470f388520309479ab0bf5e323505daf0290cd3850"
+dependencies = [
+ "darling_core",
+ "darling_macro",
+]
+
+[[package]]
+name = "darling_core"
+version = "0.14.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "109c1ca6e6b7f82cc233a97004ea8ed7ca123a9af07a8230878fcfda9b158bf0"
+dependencies = [
+ "fnv",
+ "ident_case",
+ "proc-macro2",
+ "quote",
+ "strsim",
+ "syn 1.0.109",
+]
+
+[[package]]
+name = "darling_macro"
+version = "0.14.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4aab4dbc9f7611d8b55048a3a16d2d010c2c8334e46304b40ac1cc14bf3b48e"
+dependencies = [
+ "darling_core",
+ "quote",
+ "syn 1.0.109",
+]
+
 [[package]]
 name = "deranged"
 version = "0.3.9"
@@ -347,6 +408,37 @@ dependencies = [
  "powerfmt",
 ]
 
+[[package]]
+name = "derive_builder"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8d67778784b508018359cbc8696edb3db78160bab2c2a28ba7f56ef6932997f8"
+dependencies = [
+ "derive_builder_macro",
+]
+
+[[package]]
+name = "derive_builder_core"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c11bdc11a0c47bc7d37d582b5285da6849c96681023680b906673c5707af7b0f"
+dependencies = [
+ "darling",
+ "proc-macro2",
+ "quote",
+ "syn 1.0.109",
+]
+
+[[package]]
+name = "derive_builder_macro"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ebcda35c7a396850a55ffeac740804b40ffec779b98fffbb1738f4033f0ee79e"
+dependencies = [
+ "derive_builder_core",
+ "syn 1.0.109",
+]
+
 [[package]]
 name = "dirs"
 version = "1.0.5"
@@ -512,7 +604,7 @@ checksum = "53b153fd91e4b0147f4aced87be237c98248656bb01050b96bf3ee89220a8ddb"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.39",
 ]
 
 [[package]]
@@ -700,6 +792,12 @@ dependencies = [
  "cc",
 ]
 
+[[package]]
+name = "ident_case"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b9e0384b61958566e926dc50660321d12159025e767c18e043daf26b70104c39"
+
 [[package]]
 name = "idna"
 version = "0.2.3"
@@ -829,6 +927,15 @@ version = "2.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f665ee40bc4a3c5590afb1e9677db74a508659dfd71e126420da8274909a0167"
 
+[[package]]
+name = "memoffset"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a634b1c61a95585bd15607c6ab0c4e5b226e695ff2800ba0cdccddf208c406c"
+dependencies = [
+ "autocfg",
+]
+
 [[package]]
 name = "mime"
 version = "0.3.17"
@@ -940,7 +1047,7 @@ checksum = "a948666b637a0f465e8564c73e89d4dde00d72d4d473cc972f390fc3dcee7d9c"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.39",
 ]
 
 [[package]]
@@ -1119,6 +1226,26 @@ dependencies = [
  "getrandom 0.2.11",
 ]
 
+[[package]]
+name = "rayon"
+version = "1.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c27db03db7734835b3f53954b534c91069375ce6ccaa2e065441e07d9b6cdb1"
+dependencies = [
+ "either",
+ "rayon-core",
+]
+
+[[package]]
+name = "rayon-core"
+version = "1.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ce3fb6ad83f861aac485e76e1985cd109d9a3713802152be56c3b1f0e0658ed"
+dependencies = [
+ "crossbeam-deque",
+ "crossbeam-utils",
+]
+
 [[package]]
 name = "redox_syscall"
 version = "0.1.57"
@@ -1374,7 +1501,7 @@ checksum = "43576ca501357b9b071ac53cdc7da8ef0cbd9493d8df094cd821777ea6e894d3"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.39",
 ]
 
 [[package]]
@@ -1444,6 +1571,23 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "strsim"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
+
+[[package]]
+name = "syn"
+version = "1.0.109"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72b64191b275b66ffe2469e8af2c1cfe3bafa67b529ead792a6d0160888b4237"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
 [[package]]
 name = "syn"
 version = "2.0.39"
@@ -1515,7 +1659,7 @@ checksum = "266b2e40bc00e5a6c09c3584011e08b06f123c00362c92b975ba9843aaaa14b8"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.39",
 ]
 
 [[package]]
@@ -1604,7 +1748,7 @@ checksum = "5b8a1e28f2deaa14e508979454cb3a223b10b938b45af148bc0986de36f1923b"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.39",
 ]
 
 [[package]]
@@ -1656,7 +1800,7 @@ checksum = "34704c8d6ebcbc939824180af020566b01a7c01f80641264eba0999f6c2b6be7"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.39",
 ]
 
 [[package]]
@@ -1769,7 +1913,7 @@ dependencies = [
  "once_cell",
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.39",
  "wasm-bindgen-shared",
 ]
 
@@ -1803,7 +1947,7 @@ checksum = "f0eb82fcb7930ae6219a7ecfd55b217f5f0893484b7a13022ebb2b2bf20b5283"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.39",
  "wasm-bindgen-backend",
  "wasm-bindgen-shared",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index cf1f795..8270dc5 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -25,3 +25,5 @@ serde_json = "1"
 tiktoken-rs = "0.5"
 tokio = { version = "1", features = ["full"] }
 itertools = "0.12"
+derive_builder = "0.12.0"
+rayon = "1.8.0"
diff --git a/aoc_puzzle_cache/day_5 b/aoc_puzzle_cache/day_5
new file mode 100644
index 0000000..d1aabaa
--- /dev/null
+++ b/aoc_puzzle_cache/day_5
@@ -0,0 +1,197 @@
+seeds: 3127166940 109160474 3265086325 86449584 1581539098 205205726 3646327835 184743451 2671979893 17148151 305618297 40401857 2462071712 203075200 358806266 131147346 1802185716 538526744 635790399 705979250
+
+seed-to-soil map:
+931304316 1786548802 232453384
+3500539319 2322065235 6421609
+496396007 147739714 266329192
+3169724489 768672891 39526579
+3689153715 1361862036 346985
+1936948751 3328259881 542896984
+3209251068 3154345676 173914205
+1163757700 2814318523 24125066
+2484210664 1362209021 231487475
+3991904247 2133571422 188493813
+1187882766 4045525873 83717994
+861951350 3084992710 69352966
+2715698139 2838443589 43714032
+3830303258 4025104215 20421658
+768672891 1268583577 93278459
+4180398060 2019002186 114569236
+3689500700 1593696496 10659519
+1271600760 808199470 460384107
+166497091 526585653 102729094
+3700160219 3894961176 130143039
+2966889400 2882157621 202835089
+147739714 414068906 18757377
+3850724916 4133608796 141179331
+2759412171 2328486844 183672918
+2479845735 4129243867 4364929
+3480360150 4274788127 20179169
+402636637 432826283 93759370
+3383165273 2717123646 97194877
+3506960928 1604356015 182192787
+269226185 629314747 133410452
+2943085089 3871156865 23804311
+1731984867 2512159762 204963884
+
+soil-to-fertilizer map:
+3368312743 826425240 243745914
+1045038113 3682756471 174490549
+3931158487 1530223690 363808809
+1219528662 2460222182 131099318
+3020480207 1894032499 63879875
+121779694 248970341 36319877
+1993634034 2662348686 86667553
+3612058657 1323325837 196530127
+1531175223 2604354699 57993987
+158099571 121779694 127190647
+1867147432 3317666386 126486602
+2080301587 2768963716 548702670
+1402482267 1070171154 21180243
+2959841028 4051272297 60639179
+834756529 1966243663 128160296
+3911211010 2749016239 19947477
+962916825 3857247020 82121288
+2629004257 3444152988 238603483
+826425240 1957912374 8331289
+1350627980 3939368308 51854287
+1589169210 4214533702 80433594
+2867607740 2094403959 92233288
+1669602804 1125781209 197544628
+3084360082 1519855964 10367726
+1483712212 1091351397 34429812
+3094727808 2186637247 273584935
+1423662510 3991222595 60049702
+3808588784 4111911476 102622226
+1518142024 2591321500 13033199
+
+fertilizer-to-water map:
+206818393 1973789958 18543481
+2641351404 1992333439 41420268
+58400970 2574944960 107826712
+3710426911 4065366707 42793360
+4217161704 4274048011 20919285
+1926695368 705931711 328031436
+1449580741 1210970895 50549447
+907984567 1421828853 15115545
+769748018 1108192216 102778679
+451427938 35457870 38201654
+2254726804 2033892789 137829519
+923239194 1513967644 270588891
+3753220271 4108160067 165887944
+499804857 310274559 109862756
+3061525238 3535532059 426476055
+1193828085 73659524 196024324
+872526697 0 35457870
+1766386857 1261520342 160308511
+4057593930 3283950856 159567774
+1389852409 646203379 59728332
+3919108215 3962008114 103358593
+1577153434 1784556535 189233423
+4022466808 3443518630 35127122
+489629592 1098016951 10175265
+923100112 2033753707 139082
+2392556323 2390203683 158894869
+1500130188 1436944398 77023246
+2577297600 1033963147 64053804
+609667613 2171722308 160080405
+3488001293 3061525238 222425618
+2551451192 2549098552 25846408
+4238080989 3478645752 56886307
+166227682 269683848 40590711
+0 2331802713 58400970
+225361874 420137315 226066064
+
+water-to-light map:
+1833244152 0 764535859
+212138399 2132863085 224047237
+445686952 1600446740 163005122
+3322180377 2914685303 488586806
+2739726430 3712513349 582453947
+3946546331 3589340640 8839399
+1441711040 799272484 245821386
+1038755613 1763451862 6623730
+608692074 1587251997 13194743
+701103180 2356910322 39153476
+1687532426 1045093870 145711726
+2597780011 764535859 34736625
+740256656 1490869662 54307168
+0 1920724686 212138399
+2632516636 1545176830 9229765
+668257778 1554406595 32845402
+3955385730 2739726430 39179725
+4180633986 3598180039 114333310
+3810767183 2778906155 135779148
+1291061946 1770075592 150649094
+436185636 1481368346 9501316
+1045379343 2396063798 245682603
+794563824 1237176557 244191789
+621886817 1190805596 46370961
+3994565455 3403272109 186068531
+
+light-to-temperature map:
+432141642 1268486741 19474646
+3617581823 3276436954 357008111
+3505110084 3786131308 49942802
+0 1287961387 432141642
+3096011130 1808659179 409098954
+1347993824 2675880000 161612192
+3019335150 3199760974 76675980
+3555052886 3137232037 62528937
+2778092757 1720103029 88556150
+451616288 2217758133 458121867
+1509606016 0 1268486741
+909738155 3836074110 138515824
+1048253979 2837492192 299739845
+2866648907 3633445065 152686243
+
+temperature-to-humidity map:
+646729740 1519504972 559297346
+1894539176 2990410634 44298872
+232257988 972432123 414471752
+2277879451 278205785 108711195
+1775790220 132298732 118748956
+3371687162 2663455233 326955401
+1612056920 272509895 5695890
+1208383109 3703499740 147415518
+4070380190 4053129082 69974785
+4155541210 3305585510 139426086
+81956384 386916980 150301604
+3987543096 896459472 75972651
+2148980475 1386903875 128898976
+1617752810 3445011596 154599732
+4063515747 2078802318 6864443
+2392568787 3599611328 101532389
+2386590646 4123103867 5978141
+2494101176 2122546980 187027686
+2681128862 2085666761 36880219
+4140354975 2648268998 15186235
+1772352542 3051742077 3437678
+1355798627 3850915258 202213824
+3720104770 3055179755 250405755
+3032992830 2309574666 338694332
+1206027086 3701143717 2356023
+1938838048 537218584 44257139
+1558012451 81956384 50342348
+3970510525 3034709506 17032571
+1608354799 1515802851 3702121
+1983095187 4129082008 165885288
+3698642563 251047688 21462207
+2718009081 581475723 314983749
+
+humidity-to-location map:
+971626884 4275486551 19480745
+1218249913 2090555906 502249162
+2914848039 2902831882 224865747
+3341591733 2819947352 82884530
+991107629 2592805068 227142284
+3424476263 606585628 95279547
+4279176998 2064757318 10971709
+3139713786 4068790015 201877947
+606585628 701865175 365041256
+3534582689 3291885426 744594309
+1916997152 1066906431 997850887
+1752809355 3127697629 164187797
+1720499075 4036479735 32310280
+4290148707 4270667962 4818589
+3519755810 2075729027 14826879
diff --git a/src/bin/day5.rs b/src/bin/day5.rs
index 583b328..aab9255 100644
--- a/src/bin/day5.rs
+++ b/src/bin/day5.rs
@@ -1,27 +1,251 @@
 use aoc23::prelude::*;
-use std::time::Instant;
+use derive_builder::Builder;
+use itertools::Itertools;
+use rayon::prelude::*;
+use std::{str::FromStr, time::Instant};
+
+#[derive(Debug, Builder, Clone)]
+struct Map {
+    destination_start: usize,
+    source_start: usize,
+    length: usize,
+}
+
+impl FromStr for Map {
+    type Err = BoxE;
+
+    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
+        let mut parts = s
+            .trim()
+            .split_whitespace()
+            .map(|s| s.parse::<usize>().expect("failed to parse"));
+        Ok(MapBuilder::default()
+            .destination_start(parts.next().expect("no dest"))
+            .source_start(parts.next().expect("no start"))
+            .length(parts.next().expect("no length"))
+            .build()?)
+    }
+}
+
+impl Map {
+    fn includes_source(&self, source: usize) -> bool {
+        source >= self.source_start && source < self.source_start + self.length
+    }
+
+    fn apply(&self, source: usize) -> Option<usize> {
+        if self.includes_source(source) {
+            let diff = source - self.source_start;
+            Some(self.destination_start + diff)
+        } else {
+            None
+        }
+    }
+}
+
+#[derive(Debug, Builder, Clone)]
+struct Mapper {
+    source: String,
+    destination: String,
+    maps: Vec<Map>,
+}
+
+impl FromStr for Mapper {
+    type Err = BoxE;
+
+    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
+        let mut mapper = MapperBuilder::default();
+        mapper.maps(vec![]);
+        for line in s.trim().lines() {
+            if mapper.source.is_none() {
+                let mut keys = line
+                    .split_whitespace()
+                    .next()
+                    .expect("no source-dest")
+                    .split("-to-");
+                mapper.source(keys.next().expect("no source key").to_owned());
+                mapper.destination(keys.next().expect("no destination key").to_owned());
+            } else if let Some(maps) = &mut mapper.maps {
+                maps.push(line.parse()?);
+            }
+        }
+        Ok(mapper.build()?)
+    }
+}
+
+impl Mapper {
+    fn apply(&self, source: usize) -> usize {
+        self.maps
+            .iter()
+            .find_map(|map| map.apply(source))
+            .unwrap_or(source)
+    }
+}
+
+#[derive(Debug, Builder, Clone)]
+struct Seeds {
+    source: String,
+}
+
+#[derive(Debug, Builder)]
+struct Almanac {
+    seeds: Seeds,
+    mappers: Vec<Mapper>,
+}
+
+impl Almanac {
+    fn map_source(&self, source: usize, start_key: &str, end_key: &str) -> usize {
+        let mut current_key = start_key;
+        let mut current_value = source;
+        while current_key != end_key {
+            let mapper = self
+                .mappers
+                .iter()
+                .find(|mapper| mapper.source == current_key)
+                .expect("could not find mapper");
+            current_value = mapper.apply(current_value);
+            current_key = &mapper.destination;
+        }
+        current_value
+    }
+}
+
+impl FromStr for Almanac {
+    type Err = BoxE;
+
+    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
+        let mut almanac = AlmanacBuilder::default();
+        let mut parts = s.trim().split("\n\n");
+        almanac.seeds(Seeds {
+            source: parts.next().expect("seed line missing").to_string(),
+        });
+        almanac.mappers(vec![]);
+        while let Some(mapper_section) = parts.next() {
+            if let Some(mappers) = &mut almanac.mappers {
+                mappers.push(mapper_section.parse()?);
+            }
+        }
+        Ok(almanac.build()?)
+    }
+}
 
 fn part1(input: String) -> Result<usize> {
-    let mut answer = 0;
-    println!("Input:\n{}", input);
+    // parse
+    let start = Instant::now();
+    let almanac: Almanac = input.parse()?;
+    let parsed_time = start.elapsed();
+
+    // algo
+    let start = Instant::now();
+    let answer = almanac
+        .seeds
+        .source
+        .split(":")
+        .nth(1)
+        .expect("seeds missing")
+        .trim()
+        .split_whitespace()
+        .map(|s| s.parse::<usize>().expect("failed to parse seed as number"))
+        .map(|source| almanac.map_source(source, "seed", "location"))
+        .par_bridge()
+        .min()
+        .ok_or("failed to get min location")?;
+    let algo_time = start.elapsed();
+
+    // output
+    println!("Day 5, part 1: {answer}");
+    println!("\tparse: {parsed_time:?}");
+    println!("\talgo: {algo_time:?}");
     Ok(answer)
 }
 
 fn part2(input: String) -> Result<usize> {
-    let mut answer = 0;
+    // parse
+    let start = Instant::now();
+    let almanac: Almanac = input.parse()?;
+    let parsed_time = start.elapsed();
+
+    // algo
+    let start = Instant::now();
+    let answer = almanac
+        .seeds
+        .source
+        .split(":")
+        .nth(1)
+        .expect("seeds missing")
+        .trim()
+        .split_whitespace()
+        .map(|s| s.parse::<usize>().expect("failed to parse seed as number"))
+        .tuples()
+        .flat_map(|(start, length)| start..start + length)
+        .par_bridge()
+        .map(|source| almanac.map_source(source, "seed", "location"))
+        .min()
+        .ok_or("failed to get min location")?;
+    let algo_time = start.elapsed();
+
+    // output
+    println!("Day 5, part 1: {answer}");
+    println!("\tparse: {parsed_time:?}");
+    println!("\talgo: {algo_time:?}");
     Ok(answer)
 }
 
 #[tokio::main]
 async fn main() -> Result<()> {
-    println!("Day 5");
-    println!("=====");
-
-    // let input = utils::aoc::get_puzzle_input(5).await?;
-    let input = "".to_owned();
-    let start = Instant::now();
-    println!("part 1: {}\t[{:?}]", part1(input.clone())?, start.elapsed());
-    let start = Instant::now();
-    println!("part 2: {}\t[{:?}]", part2(input.clone())?, start.elapsed());
+    let input = utils::aoc::get_puzzle_input(5).await?;
+    part1(input.clone())?;
+    part2(input.clone())?;
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    static DATA: &'static str = "seeds: 79 14 55 13
+
+seed-to-soil map:
+50 98 2
+52 50 48
+
+soil-to-fertilizer map:
+0 15 37
+37 52 2
+39 0 15
+
+fertilizer-to-water map:
+49 53 8
+0 11 42
+42 0 7
+57 7 4
+
+water-to-light map:
+88 18 7
+18 25 70
+
+light-to-temperature map:
+45 77 23
+81 45 19
+68 64 13
+
+temperature-to-humidity map:
+0 69 1
+1 0 69
+
+humidity-to-location map:
+60 56 37
+56 93 4
+";
+
+    #[test]
+    fn test_part_1() -> Result<()> {
+        assert_eq!(part1(DATA.to_owned())?, 35);
+        Ok(())
+    }
+
+    #[test]
+    fn test_part_2() -> Result<()> {
+        assert_eq!(part2(DATA.to_owned())?, 46);
+        Ok(())
+    }
+}