import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double num = sc.nextDouble();
        double result = binarySearch(num);
        System.out.printf("%.1f",result);//注意这里是printf  System.out.printf格式化输出 "%.1f"保留一位小数。
    }
    public static double binarySearch(double num) {
        double left = Math.min(-1, num);
        double right = Math.max(1, num);
        double mid = 0.0;
        //无限逼近,当right 和 left 精度小于0.0001了,说明left的值就逼近答案。
        while (right - left > 0.001) {
            mid = (right + left) / 2;
            if (mid * mid * mid > num) {
                right = mid;
            } else if (mid * mid * mid < num) {
                left = mid;
            } else {
                return mid;//相等情况,直接退出。1 或者 -1 或者 0.
            }
        }
        return left;
    }
}