(* Requires Batteries Included. *)

open Random with self_init ()

let random_num_char () =
  match int(62) with
    | n when n < 26 -> int_of_char 'a' + n
    | n when n < 26 + 26 -> int_of_char 'A' + n - 26
    | n -> int_of_char '0' + n - 26 - 26

let make_pass length =
  for i = 0 to length - 1 do
    print_char (char_of_int(random_num_char ()))
  done;
  print_newline ()

let main () =
  if Array.length Sys.argv < 2 then
    make_pass 8
  else 
    try
      make_pass (int_of_string(Sys.argv.(1)))
    with 
      | Failure "int_of_string" -> print_endline "Bad argument."; exit 1

let () = main ()