/in/foo.cc: In function 'int main()':
/in/foo.cc:53:3: error: reference to 'next' is ambiguous
   next[i]=pos[a[i]];
   ^~~~
/in/foo.cc:6:40: note: candidates are: int next [50010]
 int n,m,a[50010],c[50010],pos[1000010],next[50010],maxa;
                                        ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/algorithm:61,
                 from /in/foo.cc:2:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:208:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~
/in/foo.cc:73:8: error: reference to 'next' is ambiguous
    if (next[pre]) add(next[pre],1);
        ^~~~
/in/foo.cc:6:40: note: candidates are: int next [50010]
 int n,m,a[50010],c[50010],pos[1000010],next[50010],maxa;
                                        ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/algorithm:61,
                 from /in/foo.cc:2:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:208:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~
/in/foo.cc:73:23: error: reference to 'next' is ambiguous
    if (next[pre]) add(next[pre],1);
                       ^~~~
/in/foo.cc:6:40: note: candidates are: int next [50010]
 int n,m,a[50010],c[50010],pos[1000010],next[50010],maxa;
                                        ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/algorithm:61,
                 from /in/foo.cc:2:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:208:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~