import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in =new Scanner(System.in);
        double n=in.nextDouble();
        double l=-100000000;
        double r=1000000000;
        while (r-l>1e-8){
            double mid=(l+r)/2;
            if(mid*mid*mid>=n){
                r=mid;
            }else {
                l=mid;
            }
        }
        System.out.printf("%f",l);
    }
}