View Compilation Error

0_0_32507528_18521.cpp: In function 'int change(int)':
0_0_32507528_18521.cpp:9:9: error: 'a' was not declared in this scope
         a = n / 10;
         ^
0_0_32507528_18521.cpp: In function 'int main()':
0_0_32507528_18521.cpp:23:32: error: 'huiwen' was not declared in this scope
         while(num != huiwen(num))
                                ^