直接引入 可以像int一样操作 跟Java里的好像 但好用多了 而且是加速版的，比用字符串写的还快(用vector<int>) 还附了些奇怪的函式 有兴趣自己写BigNumber的人可以参考看看 -Can be directly introduced to operate with the same as int in Java but it seems the more useful it is to speed up version of, than to