#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
double q;
main()
{
	while(cin>>q,q>0)
	{
		double x=q/2;
		while(abs(x*x*x-q)>=1e-5*q)x=x-(x*x*x-q)/3/x/x;
		cout<<fixed<<setprecision(16)<<x<<endl;
	}
}

