hdu 2009 求数列的和

#include<iostream>
#include<math.h>
using namespace std;
int main()
{
    double m, n;
    double num, sum;
    while (cin >> m >> n)
    {
        sum = 0;
        num = m;
        int i;
        for (i = 0; i < n; i++)
        {
            sum += num;
            num = sqrt(num);
            
        }
        printf("%0.2lf\n", sum);
    }

    system("pause");
    return 0;
}