algo. cube_root

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Double flt = sc.nextDouble(), l = -10000.0, r = 10000.0;
        while (r - l > 1e-8) {
            Double mid = (l + r) / 2;
            if (mid*mid*mid >= flt) r = mid;
            else l = mid;
        }
        System.out.print(String.format("%.6f", l));
    }
}