/in/foo.cc: In function 'int dfs(int, int)':
/in/foo.cc:20:18: error: reference to 'next' is ambiguous
         int nx=x+next[i][0];
                  ^~~~
/in/foo.cc:11:5: 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:21:18: error: reference to 'next' is ambiguous
         int ny=y+next[i][1];
                  ^~~~
/in/foo.cc:11:5: 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
     ^~~~