/in/foo.cc: In function 'int main()':
/in/foo.cc:12:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (i = 0; i < s.length(); i++) {
                 ^
/in/foo.cc:17:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if (sum >= (s.length()+1) / 2) {
           ^