diff --git a/inputs/14.txt b/inputs/14.txt
new file mode 100644
index 0000000..6dba718
--- /dev/null
+++ b/inputs/14.txt
@@ -0,0 +1,102 @@
+SCSCSKKVVBKVFKSCCSOV
+
+CP -> C
+SF -> S
+BH -> F
+SS -> N
+KB -> N
+NO -> N
+BP -> F
+NK -> P
+VP -> H
+OF -> O
+VH -> O
+FV -> F
+OP -> V
+FP -> B
+VB -> B
+OK -> S
+BS -> B
+SK -> P
+VV -> H
+PC -> S
+HV -> K
+PS -> N
+VS -> O
+HF -> B
+SV -> C
+HP -> O
+NF -> V
+HB -> F
+VO -> B
+VN -> N
+ON -> H
+KV -> K
+OV -> F
+HO -> H
+NB -> K
+CB -> F
+FF -> H
+NH -> F
+SN -> N
+PO -> O
+PH -> C
+HH -> P
+KF -> N
+OH -> N
+KS -> O
+FH -> H
+CC -> F
+CK -> N
+FC -> F
+CF -> H
+HN -> B
+OC -> F
+OB -> K
+FO -> P
+KP -> N
+NC -> P
+PN -> O
+PV -> B
+CO -> C
+CS -> P
+PP -> V
+FN -> B
+PK -> C
+VK -> S
+HS -> P
+OS -> N
+NP -> K
+SB -> F
+OO -> F
+CV -> V
+BB -> O
+SH -> O
+NV -> N
+BN -> C
+KN -> H
+KC -> C
+BK -> O
+KO -> S
+VC -> N
+KK -> P
+BO -> V
+BC -> V
+BV -> H
+SC -> N
+NN -> C
+CH -> H
+SO -> P
+HC -> F
+FS -> P
+VF -> S
+BF -> S
+PF -> O
+SP -> H
+FK -> N
+NS -> C
+PB -> S
+HK -> C
+CN -> B
+FB -> O
+KH -> O
\ No newline at end of file
diff --git a/inputs/14_test.txt b/inputs/14_test.txt
new file mode 100644
index 0000000..753f029
--- /dev/null
+++ b/inputs/14_test.txt
@@ -0,0 +1,19 @@
+
+NNCB
+
+CH -> B
+HH -> N
+CB -> H
+NH -> C
+HB -> C
+HC -> B
+HN -> C
+NN -> C
+BH -> H
+NC -> B
+NB -> B
+BN -> B
+BB -> N
+BC -> B
+CC -> N
+CN -> C
\ No newline at end of file
diff --git a/src/day14.rs b/src/day14.rs
new file mode 100644
index 0000000..45cdce8
--- /dev/null
+++ b/src/day14.rs
@@ -0,0 +1,81 @@
+use std::collections::HashMap;
+
+type Transforms = HashMap<(char, char), char>;
+
+fn part_one(input: String, transforms: Transforms) -> i32 {
+    let mut input: Vec<char> = input.chars().collect();
+    for _ in 1..=10 {
+        let pairs = input.windows(2);
+        let mut next = vec![input[0]];
+        for pair in pairs {
+            let key = (pair[0], pair[1]);
+            if let Some(val) = transforms.get(&key) {
+                next.push(*val);
+            }
+            next.push(pair[1]);
+        }
+        input = next;
+    }
+    let mut counts = HashMap::<char, i32>::new();
+    for char in input {
+        if char != '\n' {
+            counts.insert(
+                char,
+                match counts.get(&char) {
+                    Some(val) => *val + 1,
+                    _ => 1,
+                },
+            );
+        }
+    }
+    counts.iter().fold(0, |max, (_, count)| {
+        let count = *count;
+        if count > max {
+            count
+        } else {
+            max
+        }
+    }) - counts.iter().fold(i32::max_value(), |min, (_, count)| {
+        let count = *count;
+        if count < min {
+            count
+        } else {
+            min
+        }
+    })
+}
+
+fn part_two(input: String, transforms: Transforms) -> u128 {
+    todo!()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn parse_input(input: &str) -> (String, Transforms) {
+        let (input, transform_list) = input.split_once("\n\n").expect("two sections");
+        let mut transforms = Transforms::new();
+        for line in transform_list.split("\n") {
+            let (input, output) = line.split_once(" -> ").expect("transform");
+            let mut chars = input.chars();
+            transforms.insert(
+                (chars.next().unwrap(), chars.next().unwrap()),
+                output.chars().next().unwrap(),
+            );
+        }
+        (input.to_owned(), transforms)
+    }
+
+    #[test]
+    fn part_one_test_sample() {
+        let (input, transforms) = parse_input(include_str!("../inputs/14_test.txt"));
+        assert_eq!(part_one(input, transforms), 1588);
+    }
+
+    #[test]
+    fn part_one_test() {
+        let (input, transforms) = parse_input(include_str!("../inputs/14.txt"));
+        assert_eq!(part_one(input, transforms), 2112);
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 0f6f11f..eebbefd 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -9,3 +9,5 @@ pub(crate) mod day1;
 pub(crate) mod day9;
 pub(crate) mod day10;
 //pub(crate) mod day11; //todo, finish day11
+pub(crate) mod day13;
+pub(crate) mod day14;