//AcWing  790 数的三次方根 
#include <iostream>
#include <iomanip> 
using namespace std;
double n;
double q(double a){
    return a * a * a;
}

int main(){
    cin >> n;
    double l = -10000,r = 10000;
    while(r - l >= 1e-8){
        double mid = (l + r) / 2;
        if(q(mid) >= n){
            r = mid;
        }else{
            l = mid;
        }
    }
    cout << fixed << setprecision(6) << l << endl;
    return 0;
}