/in/foo.cc: In function 'void add(int, int, int)':
/in/foo.cc:14:18: error: reference to 'next' is ambiguous
   node[++tot]=y; next[tot]=a[x]; a[x]=tot; len[tot]=z;
                  ^~~~
/in/foo.cc:7:16: note: candidates are: int next [10005]
 int node[Maxn],next[Maxn],a[Maxn],len[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:3:
/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:15:18: error: reference to 'next' is ambiguous
   node[++tot]=x; next[tot]=a[y]; a[y]=tot; len[tot]=z;
                  ^~~~
/in/foo.cc:7:16: note: candidates are: int next [10005]
 int node[Maxn],next[Maxn],a[Maxn],len[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:3:
/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(int, int*, int)':
/in/foo.cc:22:23: error: reference to 'next' is ambiguous
    for (i=a[q[l]];i;i=next[i])
                       ^~~~
/in/foo.cc:7:16: note: candidates are: int next [10005]
 int node[Maxn],next[Maxn],a[Maxn],len[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:3:
/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
     ^~~~