using System;

using System.Runtime.InteropServices;

public class Program

{

    public static void Main()

    {

        A.Add(11, 1002);

    }

}

public class A

{

    public static void Add(int FN , int SN , [Optional] int X )

    {

        int Sum = FN + SN + X;

        Console.WriteLine("Sum = {0}", Sum);        

    }

}