#include<iostream>

using namespace std;

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    double n;
    cin>>n;
    double l = -10000,r = 10000;
    while(r - l > 1e-7){//防止TLE
        double mid = (l + r ) / 2;
        if(mid*mid*mid<=n){
            l=mid;
        }
        else{
            r=mid;
        }
    }
    printf("%.6lf",l);
    return 0;
}