1  main()
       2  {
       3    char c;
       4    char d;
       5    int nbits;
       6    c = -1;
       7    for (nbits = 1 ; nbits < 100; nbits++) {
       8      d = (1 << nbits) - 1;
       9      if (d == c)
      10        break;
      11    }
      12    if (nbits == 100)
      13      abort();
      14    exit(0);
      15  }