diff --git a/bin/day2404.ml b/bin/day2404.ml
index a329b9b..7f7e169 100644
--- a/bin/day2404.ml
+++ b/bin/day2404.ml
@@ -43,5 +43,28 @@ let find_xmas sa =
   List.fold_left (fun acc x -> acc + search_string x "XMAS") 0 search_strings
   + List.fold_left (fun acc x -> acc + search_string x "SAMX") 0 search_strings
 
+let find_mas sa x y =
+  let find_ms a b c d =
+    sa.(y - 1).[x - 1] = a
+    && sa.(y - 1).[x + 1] = b
+    && sa.(y + 1).[x - 1] = c
+    && sa.(y + 1).[x + 1] = d
+  in
+  sa.(y).[x] = 'A'
+  && (find_ms 'M' 'M' 'S' 'S' || find_ms 'S' 'S' 'M' 'M'
+    || find_ms 'M' 'S' 'M' 'S' || find_ms 'S' 'M' 'S' 'M')
+
+let find_mases sa =
+  let acc = ref 0 in
+  for y = 1 to Array.length sa - 2 do
+    for x = 1 to String.length sa.(y) - 2 do
+      if find_mas sa x y then acc := !acc + 1
+    done
+  done;
+  !acc
+
 let sa_of_file fname = Aoc.strings_of_file fname |> Array.of_list
-let _ = Aoc.main sa_of_file [ (string_of_int, find_xmas) ]
+
+let _ =
+  Aoc.main sa_of_file
+    [ (string_of_int, find_xmas); (string_of_int, find_mases) ]