#include <bits/stdc++.h>
using namespace std;

int main()
{
	cout << fixed << setprecision(20);
	
	int q;
	while (cin >> q, q != -1.0){
		double l = 0, r = 1e9;
		for (int i = 0; i < 100; i++){
			double m = (l + r) / 2;
			if (m * m * m < q) l = m;
			else r = m;
		}
		cout << l << endl;
	}
}