import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        double n = sc.nextDouble();

        double l = -10000, r = 10000;
        while(r - l > 1e-8){
            double mid = (l + r) / 2;
            if(mid * mid * mid >= n) r = mid;
            else l = mid;
        }

        System.out.printf("%.6f\n", l);
    }
}