/in/foo.cc: In function 'int main()':
/in/foo.cc:24:13: error: reference to 'next' is ambiguous
    book[cun[next]]=0;
             ^~~~
/in/foo.cc:9:37: note: candidates are: int next
 int n,m,cun[200]={0},book[1100]={0},next=0,all=0;
                                     ^~~~
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/string:40,
                 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:25:8: error: reference to 'next' is ambiguous
    cun[next]=t;
        ^~~~
/in/foo.cc:9:37: note: candidates are: int next
 int n,m,cun[200]={0},book[1100]={0},next=0,all=0;
                                     ^~~~
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/string:40,
                 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:27:4: error: reference to 'next' is ambiguous
    next=(next+1)%n;
    ^~~~
/in/foo.cc:9:37: note: candidates are: int next
 int n,m,cun[200]={0},book[1100]={0},next=0,all=0;
                                     ^~~~
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/string:40,
                 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:27:10: error: reference to 'next' is ambiguous
    next=(next+1)%n;
          ^~~~
/in/foo.cc:9:37: note: candidates are: int next
 int n,m,cun[200]={0},book[1100]={0},next=0,all=0;
                                     ^~~~
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/string:40,
                 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
     ^~~~