/in/foo.cc: In function 'int Con(int, int)':
/in/foo.cc:103:2: error: reference to 'next' is ambiguous
  next[++tim]=first[xc],first[xc]=tim,con[tim]=yc;
  ^~~~
/in/foo.cc:98:5: note: candidates are: int next [100010]
 int next[N],first[N],con[N],tim;
     ^~~~
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:2:
/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:104:2: error: reference to 'next' is ambiguous
  next[++tim]=first[yc],first[yc]=tim,con[tim]=xc;
  ^~~~
/in/foo.cc:98:5: note: candidates are: int next [100010]
 int next[N],first[N],con[N],tim;
     ^~~~
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:2:
/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:105:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^
/in/foo.cc: In function 'int Deal(int, int)':
/in/foo.cc:113:25: error: reference to 'next' is ambiguous
  for(id=first[xd];id;id=next[id]){
                         ^~~~
/in/foo.cc:98:5: note: candidates are: int next [100010]
 int next[N],first[N],con[N],tim;
     ^~~~
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:2:
/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:119:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^