#include<iostream>
using namespace std;
double n;
const double accuary=1e-8; //精度


int main()
{
    cin>>n;
    double l=-10000,r=10000;

    while(r-l>=accuary)
    {
        double mid=(l+r)/2;
        if(mid*mid*mid<=n) l=mid;
        else r=mid;
    }

    printf("%.6lf",l);
    return 0;
}