/in/foo.cc: In function 'void add(int, int, int)':
/in/foo.cc:16:5: error: reference to 'next' is ambiguous
     next[tot]=head[x];
     ^~~~
/in/foo.cc:9:16: note: candidates are: int next [10000]
 int head[MAXN],next[MAXM],to[MAXM],dis[MAXN],w[MAXM];
                ^~~~
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 SPFA()':
/in/foo.cc:34:35: error: reference to 'next' is ambiguous
         for(int i=head[p];i!=-1;i=next[i])
                                   ^~~~
/in/foo.cc:9:16: note: candidates are: int next [10000]
 int head[MAXN],next[MAXM],to[MAXM],dis[MAXN],w[MAXM];
                ^~~~
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
     ^~~~