/in/foo.cc: In function 'int main()':
/in/foo.cc:29:32: error: no matching function for call to 'std::set<int>::find()'
    if(vis[i]==0 && a[i]=s.find())vis[i]=1;
                                ^
In file included from /usr/include/c++/6/set:61:0,
                 from /in/foo.cc:6:
/usr/include/c++/6/bits/stl_set.h:692:7: note: candidate: std::set<_Key, _Compare, _Alloc>::iterator std::set<_Key, _Compare, _Alloc>::find(const key_type&) [with _Key = int; _Compare = std::less<int>; _Alloc = std::allocator<int>; std::set<_Key, _Compare, _Alloc>::iterator = std::_Rb_tree_const_iterator<int>; std::set<_Key, _Compare, _Alloc>::key_type = int]
       find(const key_type& __x)
       ^~~~
/usr/include/c++/6/bits/stl_set.h:692:7: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/6/bits/stl_set.h:696:7: note: candidate: std::set<_Key, _Compare, _Alloc>::const_iterator std::set<_Key, _Compare, _Alloc>::find(const key_type&) const [with _Key = int; _Compare = std::less<int>; _Alloc = std::allocator<int>; std::set<_Key, _Compare, _Alloc>::const_iterator = std::_Rb_tree_const_iterator<int>; std::set<_Key, _Compare, _Alloc>::key_type = int]
       find(const key_type& __x) const
       ^~~~
/usr/include/c++/6/bits/stl_set.h:696:7: note:   candidate expects 1 argument, 0 provided