unsigned long long int power (unsigned long long int x,unsigned long long int n)
{
   unsigned long long int ans;

    if (n == 0)
    {
        return 1;
    }
    else if (n%2 != 0)
    {
        ans = power(x , (n-1)/2 );

        return x*ans*ans;
    }
    else {
        ans = power(x , n /2 );

        return ans * ans;
    }

}