namespace std {
template<class charT, class traits = char_traits<charT>>
class basic_istream;
using istream = basic_istream<char>;
using wistream = basic_istream<wchar_t>;
template<class charT, class traits = char_traits<charT>>
class basic_iostream;
using iostream = basic_iostream<char>;
using wiostream = basic_iostream<wchar_t>;
template<class charT, class traits>
basic_istream<charT, traits>& ws(basic_istream<charT, traits>& is);
template<class charT, class traits, class T>
basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>&& is, T&& x);
}