#include <float.h>
#include <math.h>
double potenz(double x, unsigned k);

double myRoot(double p, unsigned k)
{
    if(p==0)
        return 0;

    else if(p<0)
        return -1;

    else
    {
        double x_one=1;
        double x_new=1./k*((k-1)+p);

        while(fabs(x_one-x_new)/x_one>DBL_EPSILON)
        {
            x_one=x_new;
            x_new=1./k*((k-1)*x_one+p/potenz(x_one,k-1));
        }

        return x_one;
    }
}