let () = Scanf.scanf "%d %d %d %d" @@ fun h w a b ->
  for i = 0 to h - 1 do
    for j = 0 to w - 1 do
      print_char @@
      if (i < b) = (j < a)
      then '0'
      else '1'
    done;
    print_newline ()
  done
