diff --git a/2024/d25/ex1/ex1.py b/2024/d25/ex1/ex1.py
new file mode 100755
index 0000000..9e35795
--- /dev/null
+++ b/2024/d25/ex1/ex1.py
@@ -0,0 +1,40 @@
+#!/usr/bin/env python
+
+import itertools
+import sys
+
+Schematic = list[int]
+
+
+def solve(input: str) -> int:
+    def parse_schematic(input: list[str]) -> Schematic:
+        return [row.count("#") - 1 for row in list(zip(*input))]
+
+    def parse(input: str) -> tuple[list[Schematic], list[Schematic]]:
+        locks: list[Schematic] = []
+        keys: list[Schematic] = []
+
+        for schematic in input.strip().split("\n\n"):
+            if schematic.startswith("#####"):
+                locks.append(parse_schematic(schematic.splitlines()))
+            elif schematic.endswith("#####"):
+                keys.append(parse_schematic(schematic.splitlines()[::-1]))
+            else:
+                assert False  # Sanity check
+
+        return locks, keys
+
+    def fits(lock: Schematic, key: Schematic) -> bool:
+        return all(l + k < 6 for l, k in zip(lock, key))
+
+    locks, keys = parse(input)
+    return sum(fits(lock, key) for lock, key in itertools.product(locks, keys))
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()