/in/foo.cc: In function 'void add(int, int)':
/in/foo.cc:8:30: error: reference to 'next' is ambiguous
 void add(int x,int y){tot++; next[tot]=point[x]; point[x]=tot; v[tot]=y;}
                              ^~~~
/in/foo.cc:6:56: note: candidates are: int next [500003]
 int j,n,m,x[500003],y[500003],dfsn[500003],low[500003],next[500003],point[500003],v[500003],ins[500003];
                                                        ^~~~
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 'void tarjan(int)':
/in/foo.cc:13:25: error: reference to 'next' is ambiguous
  for(int i=point[x];i;i=next[i])
                         ^~~~
/in/foo.cc:6:56: note: candidates are: int next [500003]
 int j,n,m,x[500003],y[500003],dfsn[500003],low[500003],next[500003],point[500003],v[500003],ins[500003];
                                                        ^~~~
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
     ^~~~