#include <cstdio>
#include <cmath>

int main()
{
    double x;
    scanf("%lf", &x);
    
    double l = -10000, r = 10000;
    while (r - l > 1e-8)
    {
        double mid = (l + r) / 2;
        if (mid * mid * mid > x)    r = mid;
        else    l = mid;
    }
    
    printf("%.6f\n", l);
    return 0;
}