using System;


class Program
{
    class Matrix
    {
        private readonly int[] _matrix;
        public Matrix (params int[] data)
        {
            if (data == null) _matrix = new int[0];
            _matrix = data;
        }
        public int this[int i, int j]
        {
            get
            {
                if (i != j) return 0;
                return _matrix[i];
            }
            set
            {
                if (i == j) _matrix[i] = value;
            }
        }
        public int Size { get => _matrix.Length; }
       public int Track()
        {
            int sum = 0;
            for(int i=0; i<Size;i++)
            {
                sum +=_matrix[i];
            }
            return sum;
        }
        public Matrix Add(Matrix b)
        {
            if (b.Size > Size)
            {
                for (int i = 0; i < Size; i++)
                {
                    b._matrix[i] += _matrix[i];
                }
                return b;
            }
            return b.Add(this);
        }

    }

    static void Main()
    {
        Matrix m1 = new Matrix(1, 2, 3, 4, 5);
        Console.WriteLine($"Size of 1st matrix is {m1.Size}");
        Console.WriteLine($"Second element on diagonal is {m1[1, 1]}");
        Console.WriteLine($"Second element of the first row is {m1[0, 1]}");

        Matrix m2 = new Matrix(4, 3, 2, 1);
        Console.WriteLine($"The sum of the elements of the 2nd matrix located on the main diagonal is {m2.Track()}");
        Console.WriteLine($"The sum of the elements of two matrices is ");
        Matrix m3 = m2.Add(m1);
        for(int i=0; i<m3.Size;i++)
        {
            for (int j = 0; j < m3.Size; j++)
            {
                Console.Write(m3[i, j] + " ");
            }
            Console.WriteLine();
        }
        Console.ReadKey();
    }
}