/in/foo.cc: In function 'void query(int, int, int, int, int)':
/in/foo.cc:24:11: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  int mid=l+r>>1,res=0;
          ~^~
/in/foo.cc:24:17: warning: unused variable 'res' [-Wunused-variable]
  int mid=l+r>>1,res=0;
                 ^~~
/in/foo.cc: In function 'void change(int, int, int, int, int)':
/in/foo.cc:37:11: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  int mid=l+r>>1;
          ~^~
/in/foo.cc: In function 'void dfs1(int, int)':
/in/foo.cc:48:29: error: reference to 'next' is ambiguous
  for(e=first[u];v=go[e],e;e=next[e])
                             ^~~~
/in/foo.cc:14:14: note: candidates are: int next [101000]
 int first[N],next[N],go[N];
              ^~~~
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 dfs2(int, int)':
/in/foo.cc:69:29: error: reference to 'next' is ambiguous
  for(e=first[u];v=go[e],e;e=next[e])
                             ^~~~
/in/foo.cc:14:14: note: candidates are: int next [101000]
 int first[N],next[N],go[N];
              ^~~~
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 build(int, int, int)':
/in/foo.cc:82:11: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  int mid=l+r>>1;
          ~^~
/in/foo.cc: In function 'void add(int, int)':
/in/foo.cc:95:2: error: reference to 'next' is ambiguous
  next[++tot]=first[x];
  ^~~~
/in/foo.cc:14:14: note: candidates are: int next [101000]
 int first[N],next[N],go[N];
              ^~~~
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 main()':
/in/foo.cc:121:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j,k,a,b;
        ^
/in/foo.cc:121:10: warning: unused variable 'k' [-Wunused-variable]
  int i,j,k,a,b;
          ^