/in/foo.cc: In function 'void bfssum(int, int)':
/in/foo.cc:36:15: error: reference to 'next' is ambiguous
    n.x=temp.x+next[k][0];
               ^~~~
/in/foo.cc:6:5: note: candidates are: int next [4][2]
 int next[4][2]={0,1,1,0,0,-1,-1,0};
     ^~~~
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/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:37:15: error: reference to 'next' is ambiguous
    n.y=temp.y+next[k][1];
               ^~~~
/in/foo.cc:6:5: note: candidates are: int next [4][2]
 int next[4][2]={0,1,1,0,0,-1,-1,0};
     ^~~~
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/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 bfsstep()':
/in/foo.cc:76:15: error: reference to 'next' is ambiguous
    n.x=temp.x+next[i][0];
               ^~~~
/in/foo.cc:6:5: note: candidates are: int next [4][2]
 int next[4][2]={0,1,1,0,0,-1,-1,0};
     ^~~~
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/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:77:15: error: reference to 'next' is ambiguous
    n.y=temp.y+next[i][1];
               ^~~~
/in/foo.cc:6:5: note: candidates are: int next [4][2]
 int next[4][2]={0,1,1,0,0,-1,-1,0};
     ^~~~
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/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:87:19: warning: statement has no effect [-Wunused-value]
     book[n.x][n.y]==2;
     ~~~~~~~~~~~~~~^~~