#include <iostream>

using namespace std;

double n;

int main() {
    cin >> n;
    double eps = 1e-8;
    double l = -10000, r = 10000;
    while (r - l > eps) {
        double mid = (l + r) / 2;
        if (mid * mid * mid < n) l = mid;
        else r = mid;
    }
    printf("%.6f\n", l);

    return 0;
}