#include <cmath>
#include <iomanip>
#include <iostream>

using std::cbrt;
using std::cin;
using std::cout;
using std::endl;
using std::ios_base;
using std::setiosflags;
using std::setprecision;

int main() {
	int q;
	while (cin >> q && ~q) {
		cout << setiosflags(ios_base::fixed) << setprecision(6) << cbrt((double)q) << endl;
	}
}