快速幂

#include 

using namespace std;

int main()

{

    long long a, b, p;

    cin>>a>>b>>p;

    long res = 1%p;

    while(b)

      {

            if(b&1)  res = res * a %p;

            a = a *a %p;

            b = b >> 1;

      }

    cout<