#include<iostream>
#include<string>
#include<sstream>
#include<algorithm>
#include<cmath>
#include<map>
#include<set>
#include<vector>
#include<stack>
#include<queue>
#include<deque>
using namespace std;

int main() {

    int q;
    while (cin >> q && q != -1) {
        double x = q / 2.0;
        while (abs(x * x * x - q) >= 0.00001 * q) {
            x = x - (x * x * x - q) / (3 * x * x);
        }
        printf("%.6f", x);
        cout << endl;

    }
     
    return 0;
}