"f"(x): int -> int
{
  match (x) {
  case -1: return -11;
  case 0: return 00;
  case 1: return 11;
  case 2: return 22;
  case 3: return 33;
  case 4: return 44;
  case 5: return 55;
  case 6: return 66;
  case 7: return 77;
  case 8: return 88;
  case 9: return 99;
}
}