#include <iostream>
using namespace std;

double n;

double bsearch_3(double l, double r){
    const double eps = 1e-7;
    while(r - l > eps){
        double mid = (l + r) / 2;
        if(mid * mid * mid >= n) r = mid;
        else l = mid;
    }
    return l;
}

int main()
{
    cin >> n;
    printf("%.6lf", bsearch_3(-10000, 10000));
    return 0;
}