#include<iostream>
#include<cstdio>

using namespace std;

double n,ans;
double p(double a){
    return a*a*a;
}

int main(){
    cin>>n;

    double l=-22,r=22;

    while(r-l>1e-7){
       double mid=(l+r)/2;
       if((p(mid)-n)>1e-7){
           r=mid;
       }else{
           l=mid;
       }
    }
    printf("%0.6lf",l);
    return 0;

}