View Compilation Error

0_0_36070544_29999.cpp: In function 'Mat _power(Mat, int, int)':
0_0_36070544_29999.cpp:20:32: error: 'Mul' was not declared in this scope
             ans = Mul(ans, a, n);
                                ^
0_0_36070544_29999.cpp:21:24: error: 'Mul' was not declared in this scope
         a = Mul(a, a, n);
                        ^