/in/foo.cc: In function 'int main()':
/in/foo.cc:19:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < arr.length(); i++)
                     ~~^~~~~~~~~~~~~~
/in/foo.cc:15:10: warning: 'max_sp' may be used uninitialized in this function [-Wmaybe-uninitialized]
     char max_sp;
          ^~~~~~