/in/foo.cc: In function 'int Add(int, int)':
/in/foo.cc:14:5: error: reference to 'next' is ambiguous
     next[++tot]=first[u]; first[u]=tot; go[tot]=v;  
     ^~~~
/in/foo.cc:9:5: note: candidates are: int next [200010]
 int next[ONE*2],first[ONE*2],go[ONE*2],tot;  
     ^~~~
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:15:5: error: reference to 'next' is ambiguous
     next[++tot]=first[v]; first[v]=tot; go[tot]=u;  
     ^~~~
/in/foo.cc:9:5: note: candidates are: int next [200010]
 int next[ONE*2],first[ONE*2],go[ONE*2],tot;  
     ^~~~
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:16:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }  
 ^
/in/foo.cc: In function 'void Deal_first(int, int)':
/in/foo.cc:24:28: error: reference to 'next' is ambiguous
     for(int e=first[u];e;e=next[e])  
                            ^~~~
/in/foo.cc:9:5: note: candidates are: int next [200010]
 int next[ONE*2],first[ONE*2],go[ONE*2],tot;  
     ^~~~
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
     ^~~~