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diff --git a/2024/ocaml/lib/day_03/part_01.ml b/2024/ocaml/lib/day_03/part_01.ml
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+++ b/2024/ocaml/lib/day_03/part_01.ml
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+(* Day 3: Part 1 *)
+
+let find_mul text =
+  let regex_or_err = Re2.create "mul\\(([0-9]{1,3}),([0-9]{1,3})\\)" in
+  match regex_or_err with
+  | Ok regex -> (
+      let matches = Re2.get_matches regex text in
+      match matches with Ok matches -> matches | Error _ -> [])
+  | Error _ -> []
+
+let extract_pairs (matches : Re2.Match.t list) : (int * int) list =
+  List.map
+    (fun x ->
+      let left = Re2.Match.get x ~sub:(`Index 1) in
+      match left with
+      | None -> (0, 0)
+      | Some left -> (
+          let left_num = int_of_string left in
+          let right = Re2.Match.get x ~sub:(`Index 2) in
+          match right with
+          | None -> (0, 0)
+          | Some right ->
+              let right_num = int_of_string right in
+              (left_num, right_num)))
+    matches
+
+let solve input =
+  input |> find_mul |> extract_pairs
+  |> List.fold_left
+       (fun acc pair ->
+         let left, right = pair in
+         acc + (left * right))
+       0