/in/foo.cc: In function 'int main()':
/in/foo.cc:30:2: error: reference to 'max' is ambiguous
  max = 0;
  ^~~
/in/foo.cc:3:22: note: candidates are: int max
 int n, m, i, ans,a,b,max;
                      ^~~
In file included from /usr/include/c++/6/bits/char_traits.h:39:0,
                 from /usr/include/c++/6/ios:40,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/stl_algobase.h:265:5: note:                 template<class _Tp, class _Compare> const _Tp& std::max(const _Tp&, const _Tp&, _Compare)
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^~~
/usr/include/c++/6/bits/stl_algobase.h:219:5: note:                 template<class _Tp> const _Tp& std::max(const _Tp&, const _Tp&)
     max(const _Tp& __a, const _Tp& __b)
     ^~~
/in/foo.cc:33:6: error: expected '(' before 'g'
   if g(m)>g(max)
      ^
/in/foo.cc:36:7: error: reference to 'max' is ambiguous
 cout<<max<<endl;
       ^~~
/in/foo.cc:3:22: note: candidates are: int max
 int n, m, i, ans,a,b,max;
                      ^~~
In file included from /usr/include/c++/6/bits/char_traits.h:39:0,
                 from /usr/include/c++/6/ios:40,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/stl_algobase.h:265:5: note:                 template<class _Tp, class _Compare> const _Tp& std::max(const _Tp&, const _Tp&, _Compare)
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^~~
/usr/include/c++/6/bits/stl_algobase.h:219:5: note:                 template<class _Tp> const _Tp& std::max(const _Tp&, const _Tp&)
     max(const _Tp& __a, const _Tp& __b)
     ^~~