View Compilation Error

2_30942_2453961_29549.cpp: In function 'long long int modxp(long long int, long long int, long long int)':
2_30942_2453961_29549.cpp:12:34: error: 'Mul' was not declared in this scope
         if(b&1) res=Mul(res,a,mod);
                                  ^
2_30942_2453961_29549.cpp:14:22: error: 'Mul' was not declared in this scope
         a=Mul(a,a,mod);
                      ^