using System;

public class Program

{

    public static void Main()

    {

        double eps = 0.001;

        int a = int.Parse(Console.ReadLine());

        double x = a/2.0;

        double xs=x;

        do 

        {

            xs = x;

            x = (x+a/x)/2;

        }

        while(xs - x >= eps);

        Console.WriteLine(x);

    }

}