/in/foo.cc: In function 'void Add(int, int)':
/in/foo.cc:64:5: error: reference to 'next' is ambiguous
     next[++total] = head[x];
     ^~~~
/in/foo.cc:20:5: note: candidates are: int next [500000]
 int next[MAX],aim[MAX];
     ^~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/6/deque:60,
                 from /usr/include/c++/6/queue:60,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/stl_iterator_base_funcs.h:205:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~
/in/foo.cc: In function 'void Tarjan(int)':
/in/foo.cc:75:33: error: reference to 'next' is ambiguous
     for(int i = head[x]; i; i = next[i]) {
                                 ^~~~
/in/foo.cc:20:5: note: candidates are: int next [500000]
 int next[MAX],aim[MAX];
     ^~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/6/deque:60,
                 from /usr/include/c++/6/queue:60,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/stl_iterator_base_funcs.h:205:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:106:37: error: reference to 'next' is ambiguous
         for(int i = head[x]; i; i = next[i])
                                     ^~~~
/in/foo.cc:20:5: note: candidates are: int next [500000]
 int next[MAX],aim[MAX];
     ^~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/6/deque:60,
                 from /usr/include/c++/6/queue:60,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/stl_iterator_base_funcs.h:205:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~