using System;

using Puncte;

namespace Puncte

{

    public class Punct

    {

        public double x,y;

        public Punct( double  a , double b)

        {

            x=a;

            y=b;

        }

    }

}

public class Segment

{

    Puncte.Punct a,b;

    public Segment(double ax,double ay,double bx,double by)

    {

        a=new Puncte.Punct(ax,ay);

        b=new Puncte.Punct(bx,by);

    }

    public double LSegment()

    {

        return System.Math.Sqrt((b.x-a.x)*(b.x-a.x)+(b.y-a.y)*(b.y-a.y));

    }

}

public class Program

{

    public static void Main()

    {

        Segment s=new Segment(0,3,4,0);

        Console.WriteLine(s.LSegment());

    }

}