#include<iostream>
#include<cstdio>
using namespace std;

double n;

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

    return 0;
}