static void Main(string[] args)
{
int[,] matr1 = { { 1, 2, 3 },
{ 1, 2, 3 },
{ 1, 2, 3 } };
SquareMatrix<int> matrix1 = new SquareMatrix<int>(matr1);
int[,] matr2 = { { 1, 0, 0 },
{ 0, 2, 0 },
{ 0, 0, 3 } };
DiagonalMatrix<int> matrix2 = new DiagonalMatrix<int>(matr2);
int[,] matr3 = { { 1, 5, 3 },
{ 5, 2, 7 },
{ 3, 7, 3 } };
SymmetricMatrix<int> matrix3 = new SymmetricMatrix<int>(matr3);
var squar = new Listeners<int>();
squar.Register(matrix1);
squar.Register(matrix2);
squar.Register(matrix3);
matrix1[1, 2] = 3;
matrix2[2, 2] = 3;
matrix3[1, 0] = 3;
SquareMatrix<int> output = matrix1.Sum(matrix2, (x, y) => x + y);
SquareMatrix<int> output2 = matrix1.Sum(matrix2);
Console.WriteLine();
}