/in/foo.cc: In function 'int main()':
/in/foo.cc:14:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     while (pos < sentence.length())
            ~~~~^~~~~~~~~~~~~~~~~~~
/in/foo.cc:17:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if (find_pos == string::npos) break;
             ~~~~~~~~~^~~~~~~~~