xpowerywithmod.cpp

long long xpowery(long long x, long long y, long long p)
{
    long long res = 1; 
    x = x % p;
 
    while (y > 0) {
        if (y & 1)
            res = (res * x) % p;
 
        y = y >> 1; 
        x = (x * x) % p;
    }
    return res;
}