/in/foo.cc: In function 'void add(int, int, int)':
/in/foo.cc:10:3: error: reference to 'next' is ambiguous
   next[++cnt]=point[x];point[x]=cnt;e[cnt].en=y;e[cnt].v=v;
   ^~~~
/in/foo.cc:7:14: note: candidates are: int next [200020]
 int point[N],next[M<<1],cnt,x,y,v,n,m,q[N*20],f[N],dis[N][2];
              ^~~~
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 spfa()':
/in/foo.cc:18:29: error: reference to 'next' is ambiguous
     for (int i=point[u];i;i=next[i]){
                             ^~~~
/in/foo.cc:7:14: note: candidates are: int next [200020]
 int point[N],next[M<<1],cnt,x,y,v,n,m,q[N*20],f[N],dis[N][2];
              ^~~~
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
     ^~~~