#include <iostream>
#include <cmath>

using namespace std;

int main(){
	int q;
	cin >> q;
	while(q > 0){
		double x = (double)q/2;
		while(abs(pow(x,3)-q) >= 0.00001*q){
			x = x-(pow(x,3)-q)/3/pow(x,2);
		}
		cout << x <<endl;
		cin >> q;
	}
}