#include <iostream>
using namespace std;

double bsearch_3(double l ,double r,double n){
    const double eps=1e-8;
    while(r-l>eps){
        double mid=(l+r)/2;
        if(mid*mid*mid>=n) r=mid;
        else l=mid;
    }
    return l;
}

int main(){
    double x;
    scanf("%lf",&x);
    printf("%.6f\n",bsearch_3(-10000,10000,x));
    return 0;
}