快速幂，快速幂取模

ll poww(ll a,ll b)
{
    ll r=1,base=a;
    while(b){
        if(b&1) r*=base;
        base*=base;
        b>>=1;
    }
    return r;
}

 

LL qmod(LL a, LL b)
{
    if (b == 0) return 1;
    LL r = a % MOD;
    LL k = 1;
    while (b > 1){
        if ((b & 1)!=0)
            k = (k * r) % MOD;
        r = (r * r) % MOD;
        b >>= 1;
    }
    return (r * k) % MOD;
}