using System;

public class Program

{

    public static void Main()

    {

        double x1, x2, y1, y2,x3,y3,x4,y4, d,d1,d2,d3, perimeter ;

        Console.WriteLine("insert x1 for first point (X1) : " );

        x1=double.Parse(Console.ReadLine()); 

        Console.WriteLine("insert y1 for first point (y1) : " ); 

        y1=double.Parse(Console.ReadLine());

        Console.WriteLine("--------------------------------- ");

        Console.WriteLine("insert x2 for two point (X2) : " );

        x2=double.Parse(Console.ReadLine());

        Console.WriteLine("insert y2 for two point (y2) : " );

        y2=double.Parse(Console.ReadLine());

        Console.WriteLine("--------------------------------- ");

        Console.WriteLine("insert x3 for three point (X3) : " );

        x3=double.Parse(Console.ReadLine());

        Console.WriteLine("insert y3 for three point (y3) : " );

        y3=double.Parse(Console.ReadLine());

        Console.WriteLine("--------------------------------- ");

        Console.WriteLine("insert x4 for four point (X4) : " );

        x4=double.Parse(Console.ReadLine());

        Console.WriteLine("insert y4 for four point (y4) : " );

        y4=double.Parse(Console.ReadLine());

        d=Math.Sqrt(Math.Pow((x2-x1),2)+Math.Pow((y2-y1),2));

        d1=Math.Sqrt(Math.Pow((x3-x2),2)+Math.Pow((y3-y2),2));

        d2=Math.Sqrt(Math.Pow((x4-x3),2)+Math.Pow((y4-y3),2));

        d3=Math.Sqrt(Math.Pow((x4-x1),2)+Math.Pow((y4-y1),2));

        perimeter=d+d1+d2+d3;

        Console.WriteLine("--------------------------------- ");

        Console.WriteLine("محيط الشكل الرباعي هو : "+Math.Round(perimeter));

    }

}