let rec makelistNtoM n m =
  if n > m then [] else n :: makelistNtoM (n+1) m
let _ =
  let lst = Array.to_list (Array.init 9 (fun _ -> Scanf.scanf "%d " (fun x -> x))) in
  let checklst = makelistNtoM 1 10 in
  let n = List.filter (fun x -> not (List.mem x lst)) checklst in
  Printf.printf "%d\n" (List.hd n)