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

int main() {
    // 注意输入的应该是double类型
    double n;
    cin >> n;

    double l = -10000, r = 10000;
    while (r - l > 1e-8) {
        double mid = (l + r) / 2;
        if (mid * mid * mid >= n) r = mid;
        else l = mid;
    }

    printf("%.6lf", l);

    return 0;
}