#include<bits/stdc++.h>
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\n",l);
    return 0;
}