printf(stderr, "Beginning with: (%n, %n)", clock[startIndex], clock[finishIndex]);

    clock[startIndex] = clock[startIndex] ^ clock[finishIndex];
    clock[finishIndex] = clock[startIndex] ^ clock[finishIndex];
    clock[startIndex] = clock[startIndex] ^ clock[finishIndex];

    printf(stderr, "Ending with: (%n, %n)", clock[startIndex], clock[finishIndex]);