long long 模幂运算

typedef long long LL;

LL mul(LL a, LL b, LL mod) {
    LL ret = 0;
    while (b) {
        if (b & 1)
            (ret+=a)%=mod;
        b>>=1, (a<<=1)%=mod;
    }
    return ret;
}

LL mpow(LL x, LL y, LL mod) {
    LL ret = 1;
    while (y) {
        if (y & 1)
            ret = mul(ret, x, mod);
        y >>= 1, x = mul(x, x, mod);
    }
    return ret;
}

　　

直接乘的话，会爆long long ，所以采取一边加，一边模的温和运算。