using System;

    interface ITest

    {

    int Add(int a,int b);

    }

public class Calculate : ITest

{

public int Add(int a,int b)

{

return a+b;

}

}

public class Program

{

    public static void Main()

    {

    ITest objCal = new Calculate();

    Console.WriteLine(objCal.Add(5,10));

        Console.WriteLine("Hello World");

    }

}