In file included from /usr/include/c++/12/iostream:39,
                 from /in/foo.cc:1:
In member function 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(double) [with _CharT = char; _Traits = std::char_traits<char>]',
    inlined from 'int main()' at /in/foo.cc:13:35:
/usr/include/c++/12/ostream:221:25: warning: 's' may be used uninitialized [-Wmaybe-uninitialized]
  221 |       { return _M_insert(__f); }
      |                ~~~~~~~~~^~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:7:18: note: 's' was declared here
    7 |     double a,m,k,s;
      |                  ^