/in/foo.cc: In function 'void solve(int, int)':
/in/foo.cc:42:8: error: reference to 'next' is ambiguous
  if(!b[next[pos]]) 
        ^~~~
/in/foo.cc:13:11: note: candidates are: int next [200005]
 int fa[N],next[N],h[N];
           ^~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/6/algorithm:61,
                 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:43:10: error: reference to 'next' is ambiguous
    solve(next[pos],sum+1);
          ^~~~
/in/foo.cc:13:11: note: candidates are: int next [200005]
 int fa[N],next[N],h[N];
           ^~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/6/algorithm:61,
                 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:45:18: error: reference to 'next' is ambiguous
   int k=h[pos]-h[next[pos]]+1;
                  ^~~~
/in/foo.cc:13:11: note: candidates are: int next [200005]
 int fa[N],next[N],h[N];
           ^~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/6/algorithm:61,
                 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 'int main()':
/in/foo.cc:57:4: error: reference to 'next' is ambiguous
    next[i]=x;
    ^~~~
/in/foo.cc:13:11: note: candidates are: int next [200005]
 int fa[N],next[N],h[N];
           ^~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/6/algorithm:61,
                 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
     ^~~~