#include <iostream>
#include <cmath>
#include <cstdio>
//#include <fstream>

using namespace std;

int main()
{
//	cut here before submit 
//	freopen("testcase.tr", "r", stdin);
	double q;

	while (cin >> q &&  q != -1.0 ){
		double x = q/2.;
		while (fabs (x*x*x - q) >= 0.00001*q  ){
			double y = (x*x*x - q)/(3.*x*x);
			x = x - y;
		} // end while

		printf ("%.6f\n", x);
	} // end loop
		
	return 0;
}