View Compilation Error

1_733_2728_7985.cpp:13:26: error: array must be initialized with a brace-enclosed initializer
  long long a[3][3] = { 0 };
                          ^
1_733_2728_7985.cpp: In function 'int main()':
1_733_2728_7985.cpp:57:10: error: no match for 'operator*' (operand types are 'Matrix' and 'Matrix')
    x = x * y.pow(n-1);
          ^
1_733_2728_7985.cpp:57:10: note: candidate is:
1_733_2728_7985.cpp:19:8: note: Matrix Matrix::operator*(Matrix&)
 Matrix Matrix::operator*(Matrix& B) {
        ^
1_733_2728_7985.cpp:19:8: note:   no known conversion for argument 1 from 'Matrix' to 'Matrix&'