#include<iostream>
using namespace std;


double n;
int main(){
    cin>>n;
    double l=-10000,r=10000;
    while(r-l>1e-8){
        double mid=(l+r)/2.0;
        if((double)mid*mid*mid>=n)r=mid;
        else l=mid;
    }
    printf("%.6lf",r);
    return 0;
}