/in/foo.cc: In function 'int main()':
/in/foo.cc:13:12: error: 'max' was not declared in this scope
     char A[max];
            ^~~
/in/foo.cc:19:17: error: 'A' was not declared in this scope
     scanf("%s", A);
                 ^
/in/foo.cc:20:17: error: 'B' was not declared in this scope
     scanf("%s", B);
                 ^
/in/foo.cc:24:28: error: 'concates' was not declared in this scope
         concates(newA, A, B);
                            ^