/in/foo.cc: In function 'void read(int&)':
/in/foo.cc:19:11: warning: variable 'f' set but not used [-Wunused-but-set-variable]
  x=0;bool f=false;char ch=getchar();
           ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:27:7: error: 'A' was not declared in this scope
  read(A);read(B);long long ans;
       ^
/in/foo.cc:27:15: error: 'B' was not declared in this scope
  read(A);read(B);long long ans;
               ^