using System;

public class Test
{
    public static void Main()
    {
        double x = double.Parse(Console.ReadLine());
        double y = 1;
        if(x < -4){
            y = 2 * x + 1;
        }
        if(x >= -4 && x <= 5){
            y = Math.Sqrt((x * x) + 3);
        }
        else{
            y = x / ((2 * x) + 1);
        }
        Console.WriteLine(y);
    }
}