#include<iostream>
using namespace std;

int main()
{
    double x;
    cin >> x;

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

    printf("%lf",l);
    return 0;
}