/in/foo.cc: In function 'void link(int, int)':
/in/foo.cc:26:32: error: reference to 'next' is ambiguous
 inline void link(int x,int y){ next[++ecnt]=first[x]; first[x]=ecnt; to[ecnt]=y; }
                                ^~~~
/in/foo.cc:17:26: note: candidates are: int next [600011]
 int n,m,ecnt,first[MAXN],next[MAXM],to[MAXM],f[MAXN][20],deep[MAXN],ans[MAXN],val[MAXN],tong[MAXN],MAXD,w[MAXN],num[1000011];
                          ^~~~
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 init(int, int)':
/in/foo.cc:36:28: error: reference to 'next' is ambiguous
     for(int i=first[x];i;i=next[i]) {
                            ^~~~
/in/foo.cc:17:26: note: candidates are: int next [600011]
 int n,m,ecnt,first[MAXN],next[MAXM],to[MAXM],f[MAXN][20],deep[MAXN],ans[MAXN],val[MAXN],tong[MAXN],MAXD,w[MAXN],num[1000011];
                          ^~~~
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:44:5: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
     if(deep[x]<deep[y]) swap(x,y); int t=0; while((1<<t)<=deep[x]) t++; t--;
     ^~
/in/foo.cc:44:36: 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=0; while((1<<t)<=deep[x]) t++; t--;
                                    ^~~
/in/foo.cc:45:5: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
     for(int i=t;i>=0;i--) if(deep[x]-(1<<i)>=deep[y]) x=f[x][i]; if(x==y) return y;
     ^~~
/in/foo.cc:45:66: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
     for(int i=t;i>=0;i--) if(deep[x]-(1<<i)>=deep[y]) x=f[x][i]; if(x==y) return y;
                                                                  ^~
/in/foo.cc:46:5: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
     for(int i=t;i>=0;i--) if(f[x][i]!=f[y][i]) x=f[x][i],y=f[y][i]; return f[x][0];
     ^~~
/in/foo.cc:46:69: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
     for(int i=t;i>=0;i--) if(f[x][i]!=f[y][i]) x=f[x][i],y=f[y][i]; return f[x][0];
                                                                     ^~~~~~
/in/foo.cc: In function 'void dfs(int, int)':
/in/foo.cc:51:28: error: reference to 'next' is ambiguous
     for(int i=first[x];i;i=next[i]) {
                            ^~~~
/in/foo.cc:17:26: note: candidates are: int next [600011]
 int n,m,ecnt,first[MAXN],next[MAXM],to[MAXM],f[MAXN][20],deep[MAXN],ans[MAXN],val[MAXN],tong[MAXN],MAXD,w[MAXN],num[1000011];
                          ^~~~
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, int)':
/in/foo.cc:61:28: error: reference to 'next' is ambiguous
     for(int i=first[x];i;i=next[i]) {
                            ^~~~
/in/foo.cc:17:26: note: candidates are: int next [600011]
 int n,m,ecnt,first[MAXN],next[MAXM],to[MAXM],f[MAXN][20],deep[MAXN],ans[MAXN],val[MAXN],tong[MAXN],MAXD,w[MAXN],num[1000011];
                          ^~~~
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 work()':
/in/foo.cc:72:5: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
     for(int i=1;i<=n;i++) w[i]=getint(); ecnt=0;
     ^~~
/in/foo.cc:72:42: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
     for(int i=1;i<=n;i++) w[i]=getint(); ecnt=0;
                                          ^~~~