std::ostream& operator<<(std::ostream& os, const Matrix& A)
{
    for (int i = 0; i < A.size; i++)
    {
        os << std::endl;
        for (int j = 0; j < A.size; j++)
            os<<  std::setw(5) << A.matrix[i][j];
    }
    return os;
}

std::istream& operator>>(std::istream& is, Matrix& A)
{
    std::cout << "Input matrix size: ";
    is >> A.size;
    std::cout << std::endl;

    std::cout << "Initialize matrix:" << std::endl;
    for (int i = 0; i < A.size; i++)
    {
        for (int j = 0; j < A.size; j++)
        {
            is >> A.matrix[i][j];
        }
    }
    return is;

}