View Compilation Error

0_0_18115369_15615.cpp: In function 'int main()':
0_0_18115369_15615.cpp:149:23: error: no match for 'operator*' (operand types are 'Matrix' and 'Matrix')
   ans = quickpow(a, m)*b;
                       ^
0_0_18115369_15615.cpp:149:23: note: candidate is:
0_0_18115369_15615.cpp:49:16: note: Matrix operator*(Matrix&, Matrix&)
  friend Matrix operator*(Matrix &m1, Matrix &m2) {
                ^
0_0_18115369_15615.cpp:49:16: note:   no known conversion for argument 1 from 'Matrix' to 'Matrix&'