// External Function (prototype)
printf(fmt, args);
atoi(str);

fact1(n) {
  var r;
  if (n == 0) r = 1;
  else r = n * fact1(n - 1);
  return r;
}

fact2(n) {
  var r; r = 1;
  while (n > 0) {
    r = r * n;
    n = n - 1;
  }
  return r;
}

fact3(n) {
  var i,r; i = r = 1;
  while (i <= n) {
    r = r * i;
    i = i + 1;
  }
  return r;
}

// Main routine
main(argc, argv) {
  var n;

  if (argc < 2) {
    printf("usage: facts n\n");
    return 1;
  }

  n = atoi(argv[1]);
  printf("fact1: %d\n", fact1(n));
  printf("fact2: %d\n", fact2(n));
  printf("fact3: %d\n", fact3(n));
  return 0;
}