求数列的和

#include <stdio.h>
#include <math.h>
double zxd (int m, int n);
int main()
{
    int m, n;
    while (scanf("%d %d", &n, &m)!= EOF)
    {
        double y = zxd(n,m);
        printf("%.2lf\n",y);
    }
    return 0;
}
double zxd(int n, int m)
{
    int i;
    double x,sum;
    x = n;
    sum = n;
    for(i = 1 ; i < m ; i++)
    {

        x  = sqrt(x);
        sum = sum + x;

    }
    return sum;
}