#include <iostream>
using namespace std;

double x;

int main(void)
{
    scanf("%lf", &x);
    double l = -1e4, r = 1e4;
    while(r - l > 1e-8)
    {
        double mid = (l + r) / 2;
        if(mid * mid * mid >= x)
            r = mid;
        else
            l = mid; //! 浮点数不需要加一
    }
    printf("%lf\n", l);
    return 0;
}