万能头文件是#include<bits/stdc++.h>
//唉，为什么有时候不能用万能库！！！！
附赠
```cpp
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
#include<cmath>
#include<ctime>
#include<cctype>
#include<iomanip>
#include<algorithm>
```
by Hongyx @ 2017-07-31 22:42:42