#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;

int main()
{	
	double q;

	cin >> q;

	while (q > 0) {
		double d = q, x = q / 2;

		while (d >= 0.00001 * q) {
			x = x - (pow(x, 3) - q) / (3 * x * x);
			d = abs(pow(x, 3) - q);
		}

		cout << fixed << setprecision(7) << x << endl;

		cin >> q;
	}

	return 0;
}

