using System;

​

public class Program

{

    static private float slope(float x1, float x2, float y1, float y2)

    {

        float m = (y2 - y1) / (x2 - x1);

        reutrn m;

    }

​

    public static void Main()

    {

        float input1 = float.Parse(Console.ReadLine());

        float input2 = float.Parse(Console.ReadLine());

        float input3 = float.Parse(Console.ReadLine());

        float input4 = float.Parse(Console.ReadLine());

        Console.WriteLine(slope(input1, input2, input3, input4));

    }

}