#include <iostream>

using namespace std;

double func(double x)
{
    return x * x * x;
}

int main()
{
    double m;
    scanf("%lf", &m);
    double l = 0, r = m;
    if(r > -1 && r < 0) r = -1;
    if(r > 0 && r < 1)  r = 1; //其实直接l = -100, r = 100 即可，左右的边界没有必要仔细讨论，因为二分最后都是到那个精度
    while(r - l > 1e-8)
    {
        double mid = (l + r)/2;
        if(func(mid) > m) r = mid;
        else l = mid;
    }
    while(l - r > 1e-8)
    {
        double mid = (l + r)/2;
        if(func(mid) < m)  r = mid;
        else l = mid;
    }
    printf("%lf", l);
}