#include<cstdio>
#include<cmath>
using namespace std;
int Q;
double q,x,eps;
int main()
{
	for(;scanf("%d",&Q),Q!=-1;)
	{
		q=1.0*Q;
		eps=q*0.00001;
		x=1.0*Q/2;
		for(;abs(pow(x,3)-Q)>=eps;)
		{
			x=x-(pow(x,3)-Q)/(3*pow(x,2));
		}
		printf("%lf\n",x);
	}
	return 0;
}