/in/foo.cc: In function 'void add(int, int)':
/in/foo.cc:24:2: error: reference to 'next' is ambiguous
  next[cnt] = p[w];
  ^~~~
/in/foo.cc:18:42: note: candidates are: int next [1010025]
 int p[maxn * maxn] , temp[maxn * maxn] , next[maxn * maxn];
                                          ^~~~
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:77:31: error: reference to 'next' is ambiguous
    for (int k = p[j]; k ; k = next[k])
                               ^~~~
/in/foo.cc:18:42: note: candidates are: int next [1010025]
 int p[maxn * maxn] , temp[maxn * maxn] , next[maxn * maxn];
                                          ^~~~
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
     ^~~~