using System;

public class Program

{

    public static void Main()

    {

            int[,] matrix = {

            { 1, 2, 3, },

            { 4, 5, 6, },

            { 7, 8, 9  },

        };

        int sum = 0;

    for (int a = 0; a < matrix.GetLength(0); a++)

        {

            sum = sum + matrix[a,a];

        }

    Console.WriteLine($"Sum of diagonal elements: {sum}");

    }

}