/in/foo.cc: In function 'void add(int, int)':
/in/foo.cc:10:23: error: reference to 'next' is ambiguous
 void add(int x,int y){next[++cnt]=point[x];point[x]=cnt;e[cnt].en=y;}
                       ^~~~
/in/foo.cc:6:28: note: candidates are: int next [1200020]
 int m,now,deep[N],point[N],next[N<<1],cnt,ff,f[N],fa[N][20],n,a[N],x,y;
                            ^~~~
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 dfs(int)':
/in/foo.cc:16:27: error: reference to 'next' is ambiguous
   for (int i=point[x];i;i=next[i])
                           ^~~~
/in/foo.cc:6:28: note: candidates are: int next [1200020]
 int m,now,deep[N],point[N],next[N<<1],cnt,ff,f[N],fa[N][20],n,a[N],x,y;
                            ^~~~
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 'int lca(int, int)':
/in/foo.cc:24:4: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
    if (deep[x]<deep[y])  swap(x,y);int t=deep[x]-deep[y];
    ^~
/in/foo.cc:24:36: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if'
    if (deep[x]<deep[y])  swap(x,y);int t=deep[x]-deep[y];
                                    ^~~