#include<iostream>


using namespace std;


int main()//二分
{
    double n;
    scanf("%lf",&n);//用%lf，用f输出0.000000
    double l=-100000,r=100000;
    while(r-l>1e-8)
    {   
        double mid=(l+r)/2;
        if(mid*mid*mid >= n)r=mid;
        else l=mid;

    }

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