/in/foo.cc: In function 'int get_max(std::vector<std::vector<int> >&, std::vector<std::vector<int> >&, int, int)':
/in/foo.cc:46:47: error: no match for call to '(std::ostream {aka std::basic_ostream<char>}) (std::vector<int>&, std::vector<int>&)'
   46 |                                 int sum = cout(ball_left, ball_right);
      |                                           ~~~~^~~~~~~~~~~~~~~~~~~~~~~