using System;

​

        class Line

        {

            private double xi, yi;

            private double xf, yf;

            public Line (double x1, double y1, double x2 , double y2)

            {

               xi = x1 ; yi = y1;

               xf = x2 ;yf = y2;

                Console.WriteLine("double Constructor");

             }

            public Line (int x1, int y1, int x2 , int y2)

            {

               xi = x1 ; yi = y1;

               xf = x2 ;yf = y2;

                Console.WriteLine("int Constructor");

             }

            public double Length()

             {

                  //return (Math.Sqrt(Math.Pow((xi-xf),2)+ Math.Pow((yi-yf),2)));

                  return (Math.Sqrt(Math.Pow(xi-xf,2)+ Math.Pow(yi-yf,2)));

            }

            public void print()

                  {

                     Console.WriteLine("first point : ({0},{1}), second point : ({2},{3})",xi , yi , xf , yf);

                  }

            public double mel()

            {

                return ((yf - yi)/(xf - xi));

            }

            public void ChangeY2(double yn)

            {

                yf = yn;

            }

            public override string ToString()

            {

                return "first point is ("+this.xi+","+this.yi+"), second point is: ("+this.xf+","+this.yf+")!!!!!";

            }

        }

public class Program

{

    public static void Main()

    {

        //Line line1 = new Line(0,0,3,4);

        //Console.WriteLine("The length of Line 1 is : {0}",line1.Length());

        //Line line1 = new Line(2,4,2,4);

        //line1.print();

        //Console.WriteLine("The length of Line 1 is : {0}",line1.Length());

        int xi,xii,yi,yii;

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

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

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

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

        //Line line2 = new Line(0,0,5,5);

        Line line2 = new Line(xi,yi,xii,yii);

        line2.print();

        Console.WriteLine("The length of Line 1 is : {0}",line2.Length());

        Console.WriteLine("================");

        Console.WriteLine("the mel of Line is {0}", line2.mel());

        Console.WriteLine("The length of Line 1 is : {0}",line2.Length());

        Console.WriteLine("================");

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

        line2.ChangeY2(yii);

        line2.print();

        Console.WriteLine("the new mel of Line is {0}", line2.mel());

        Console.WriteLine("The length of Line 1 is : {0}",line2.Length());

        Console.WriteLine("================");

        Console.WriteLine(line2.ToString());

    }

}