#include<iostream>
using namespace std;
int main()
{
    double n;
    cin>>n;
    double l = -10000, r = 10000;

    while(r - l >= 1e-8){
        double mid = (l + r) / 2.0 ;
        if (mid * mid * mid >= n)
            r = mid;
        else
            l = mid;
        }

    printf("%lf\n", l);
    return 0;
}