/in/foo.cc: In function 'void addedge(int, int, int)':
/in/foo.cc:49:2: error: reference to 'next' is ambiguous
  next[++tot]=g[From];
  ^~~~
/in/foo.cc:23:16: note: candidates are: int next [1000010]
 int g[N],to[M],next[M],v[M],n,m,tot,fa[N],tmp,ans1,ans2,ma[N],mi[N],num[N];
                ^~~~
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: In function 'void dfs(int)':
/in/foo.cc:59:24: error: reference to 'next' is ambiguous
  for (int i=g[now];i;i=next[i]){
                        ^~~~
/in/foo.cc:23:16: note: candidates are: int next [1000010]
 int g[N],to[M],next[M],v[M],n,m,tot,fa[N],tmp,ans1,ans2,ma[N],mi[N],num[N];
                ^~~~
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
     ^~~~