#include<iostream>
#include<cstdio>
#include<ctime>
#include<cstdlib>
#include<cstring>
#include<string>
#include<cmath>
#include<fstream>
#include<windows.h>
#include<queue>
#include<algorithm>
namespace std
{
	
	bool isprime(int z)
	{
		if(z<2)
			return false;
		if(z==2)
			return true;
		for(int i=2;i*i<=z;++i)
		{
			if(z%i==0)
				return false;
		}
		return true;
	}
	unsigned long long fac(int n)
	{
		unsigned long long sum=1;
		for(int i=1;i<=n;++i)
			sum*=i;
		return sum;
	}
	
}