/in/foo.cc: In function 'void build(int, int, int)':
/in/foo.cc:28:5: error: reference to 'next' is ambiguous
     next[num] = p[x];  
     ^~~~
/in/foo.cc:21:5: note: candidates are: int next [10010]
 int next[10010],to[10010],val[10010],p[10010]; 
     ^~~~
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/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 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 cost(int, int)':
/in/foo.cc:57:39: error: reference to 'next' is ambiguous
         for(int i = p[now.v]; i ; i = next[i])  
                                       ^~~~
/in/foo.cc:21:5: note: candidates are: int next [10010]
 int next[10010],to[10010],val[10010],p[10010]; 
     ^~~~
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/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 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:48:9: warning: unused variable 'flag' [-Wunused-variable]
     int flag,minn;  
         ^~~~
/in/foo.cc:48:14: warning: unused variable 'minn' [-Wunused-variable]
     int flag,minn;  
              ^~~~