Number Theory rapid power, use a sieve algorithm

Fast power

void Pow(int a,int b,int Mod)
{
    int ans=1%Mod;
    for(; b; b>>=1)
    {
        if(b&1)
        {
            ans=(long long)ans*a%Mod;
        }
        a=(long long)a*a%Mod;
    }
    return ans;
}