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;
}
}