using System;

public class Program

{

    public static void Main()

    {

        point_2d P1, P2;

​

        P1 = InputPoint();

        P2 = InputPoint();

​

        Console.WriteLine("Distance between 2 points is: {0}", distance_2d(P1, P2));

​

    }

    struct point_2d

        {

            public int x;

            public int y;

        }

​

​

        static point_2d InputPoint()

        {

            point_2d kq;

​

            Console.WriteLine("Nhap X");

            kq.x= int.Parse(Console.ReadLine());

​

            Console.WriteLine("Nhap Y");

            kq.y = int.Parse(Console.ReadLine());

​

            return kq;

        }

​

        static double distance_2d(point_2d point1, point_2d point2)

        {

            double sumSquare = Math.Pow(point1.x - point2.x, 2) + Math.Pow(point1.y - point2.y, 2);

            return Math.Sqrt(sumSquare);

        }

}