#include <bits/stdc++.h>
using namespace std;

int main(){
//    int a;
    double b,c;
    while(cin>>b){
        c=b/2;
        while(fabs(c*c*c-b)>=b*1e-5){
            c=c-(c*c*c-b)/(3*c*c);
        }
        cout<<c<<endl;
    }
}