let sample_list = [
    1721;
    979;
    366;
    299;
    675;
    1456;
]

let load_list filename =
  let lines = ref [] in
  let f = open_in filename in
  try
    while true
    do
      lines := int_of_string (input_line f) :: !lines
    done; !lines
  with End_of_file ->
        close_in f;
        List.rev !lines


let (>>=) list fn = let _ = List.map fn list in None

let part_one source =
  let res = Base.With_return.with_return (fun r ->
    source >>= fun a ->
    source >>= fun b ->
      if a != b && a + b == 2020 then r.return (Some (a, b))
    ) in
  match res with
  | None -> Printf.printf "Unable to find result\n"
  | Some (x, y) -> Printf.printf "Got (%d * %d) = %d\n" x y (x * y)

let part_two source =
  let res = Base.With_return.with_return (fun r ->
    source >>= fun a ->
    source >>= fun b ->
    source >>= fun c ->
      if a != b && b != c && a != c && a + b + c == 2020 then r.return (Some (a, b, c))
    ) in
  match res with
  | None -> Printf.printf "Unable to find result\n"
  | Some (x, y, z) ->
     Printf.printf "Got (%d * %d * %d) = %d\n" x y z (x * y * z)

let main() =
  let source = load_list "input" in
  part_one source;
  part_two source

let () = main()