#include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>
#include <sstream>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <numeric>
#include <cmath>
#include <climits>
#include <limits>
#include <cfloat>
#include <fstream>
using namespace std;
//#define EPS 1E-6
int main()
{
//	cut here before submit 
//	freopen("testcase.tr", "r", stdin);
	string str = "";
	while (getline (cin, str ) ){
		double q;
		stringstream ss(str);
		ss >> q;
		if (q == -1.0){
			break;
		} // end if

		double x = q/2.;

//		cout << "x: " << x << endl;
		while (fabs (x*x*x - q) >= 0.00001*q  ){
			double y = (x*x*x - q)/(3.*x*x);
			x = x - y;
//			cout << "x: " << x << endl;
//			printf ("x: %.6f\n", x);
		} // end while

		printf ("%.6f\n", x);

//		cout << x << endl;

	} // end loop

//	cout << res << endl;	
		
	return 0;
}