diff --git a/day14/day14.py b/day14/day14.py
new file mode 100755
index 0000000..e6b2403
--- /dev/null
+++ b/day14/day14.py
@@ -0,0 +1,68 @@
+#!/usr/bin/env python3
+import sys
+from collections import defaultdict, Counter
+from typing import DefaultDict, Mapping
+from copy import deepcopy
+
+
+def apply_rules(template: str, rules: Mapping[str, str]) -> str:
+    # sliding window babey
+    new = ""
+    for i in range(len(template) - 1):
+        new += template[i] + rules[template[i : i + 2]]
+    return new + template[-1]
+
+
+def part1(template: str, rules: Mapping[str, str]):
+    for i in range(10):
+        template = apply_rules(template, rules)
+    counts: DefaultDict[str, int] = defaultdict(lambda: 0)
+    for c in template:
+        counts[c] += 1
+    counts_sorted = sorted(counts.items(), key=lambda pair: pair[1])
+    _, least = counts_sorted[0]
+    _, most = counts_sorted[-1]
+    print(most - least)
+
+
+def part2(template: str, rules: Mapping[str, str]):
+    # Apply rules with counts instead of building a string
+    counts: Counter = Counter()
+
+    for i in range(len(template) - 1):
+        counts[template[i : i + 2]] += 1
+
+    for _ in range(40):
+        new_counts: Counter = Counter()
+        for pair, count in counts.items():
+            # Create the two new pairs, and remove the old one
+            rule = rules[pair]
+            p1 = pair[0] + rule
+            p2 = rule + pair[1]
+            # Subtract from this pair, and then add the new ones
+            new_counts[p1] += counts[pair]
+            new_counts[p2] += counts[pair]
+        counts = new_counts
+    # Count all the letters, only using the first character.
+    # If we count the second character, we double-count.
+    letters: Counter = Counter()
+    for pair in counts:
+        letters[pair[0]] += counts[pair]
+    # We just need to count the last character in the original template - since this never changes.
+    letters[template[-1]] += 1
+    print(max(letters.values()) - min(letters.values()))
+
+
+template = sys.stdin.readline().strip()
+# blank
+sys.stdin.readline()
+rules = {
+    rule: translate.strip()
+    for rule, translate in map(lambda line: line.split(" -> "), sys.stdin)
+}
+
+
+print("Part 1")
+part1(template, rules)
+print("Part 2")
+part2(template, rules)
diff --git a/day14/example.txt b/day14/example.txt
new file mode 100644
index 0000000..6c1c3a1
--- /dev/null
+++ b/day14/example.txt
@@ -0,0 +1,18 @@
+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/day14/input.txt b/day14/input.txt
new file mode 100644
index 0000000..5fef7e8
--- /dev/null
+++ b/day14/input.txt
@@ -0,0 +1,102 @@
+SHHBNFBCKNHCNOSHHVFF
+
+CK -> N
+VP -> B
+CF -> S
+FO -> V
+VC -> S
+BV -> V
+NP -> P
+SN -> C
+KN -> V
+NF -> P
+SB -> C
+PC -> B
+OB -> V
+NS -> O
+FH -> S
+NK -> S
+HO -> V
+NV -> O
+FV -> O
+FB -> S
+PS -> S
+FN -> K
+HS -> O
+CB -> K
+HV -> P
+NH -> C
+BO -> B
+FF -> N
+PO -> F
+BB -> N
+PN -> C
+BP -> C
+HN -> K
+CO -> P
+BF -> H
+BC -> S
+CV -> B
+VV -> F
+FS -> B
+BN -> P
+VK -> S
+PV -> V
+PP -> B
+PH -> N
+SS -> O
+SK -> S
+NC -> P
+ON -> F
+NB -> N
+CC -> N
+SF -> H
+PF -> H
+OV -> O
+KH -> C
+CP -> V
+PK -> O
+KC -> K
+KK -> C
+KF -> B
+HP -> C
+FK -> H
+BH -> K
+VN -> H
+OO -> S
+SC -> K
+SP -> B
+KO -> V
+KV -> F
+HK -> N
+FP -> N
+NN -> B
+VS -> O
+HC -> K
+BK -> N
+KS -> K
+VB -> O
+OH -> F
+KB -> F
+KP -> H
+HB -> N
+NO -> N
+OF -> O
+BS -> H
+VO -> H
+SH -> O
+SV -> K
+HF -> C
+CS -> F
+FC -> N
+VH -> H
+OP -> K
+OK -> H
+PB -> K
+HH -> S
+OC -> V
+VF -> B
+CH -> K
+CN -> C
+SO -> P
+OS -> O
\ No newline at end of file