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}");