using System;

public class Program

{

    public static void Main()

    {

        Console.Write("xA : ");

        double xA = double.Parse(Console.ReadLine());

        Console.Write("yA : ");

        double yA = double.Parse(Console.ReadLine());

        Console.Write("xB : ");

        double xB = double.Parse(Console.ReadLine());

        Console.Write("yB : ");

        double yB = double.Parse(Console.ReadLine());

        double X = (xA+xB) / 2;

        double Y = (yA+yB) / 2;

        Console.WriteLine("Le milieu du segment [AB] est I : ("+ X + "," + Y +")");

        double D = (xB - xA) * (xB - xA) + (yB - yA) * (yB - yA);

        Console.WriteLine("Le carré de la distance entre A et B est d(A,B)^2 = " + D);

    }

}