hdu1097A hard puzzle

#include <iostream>
using namespace std;
int main()
{
    long long n,m,i,mul;
    while(cin >> n >> m)
    {
        mul = 1;
        m = m % 4;        //找规律，一个数的n次方。。它的个位数四次一循环
        if(!m)
        m += 4;
        for(i = 0 ; i < m ; ++i)
        {
            mul = mul * n % 10;
        }
        cout << mul % 10 << endl; 
    }
    return 0;
}