/in/foo.cc: In function 'void ins(int, int)':
/in/foo.cc:18:2: error: reference to 'next' is ambiguous
  next[tot]=first[z];
  ^~~~
/in/foo.cc:12:42: note: candidates are: int next [2005]
 int tot,first[2010527],px[2005],py[2005],next[2005];
                                          ^~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/6/bits/char_traits.h:39,
                 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_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 find(int, int)':
/in/foo.cc:24:25: error: reference to 'next' is ambiguous
  for(int p=first[z];p;p=next[p])
                         ^~~~
/in/foo.cc:12:42: note: candidates are: int next [2005]
 int tot,first[2010527],px[2005],py[2005],next[2005];
                                          ^~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/6/bits/char_traits.h:39,
                 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_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
     ^~~~