#include <iostream>
#include <cstdio>

using namespace std;

int main()
{
    double n;
    cin >> n;
    double l=-10000,r=10000;
    while(r-l>1e-8)
    {
        double mid= (l + r) / 2;
        if(mid * mid * mid >= n) r=mid;
        else l=mid;
    }
    printf("%lf\n",l);
    return 0;
}