/in/foo.cc: In function 'void init()':
/in/foo.cc:25:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i=0,j; i<s.length(); i++) {
                     ~^~~~~~~~~~~
/in/foo.cc:28:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             while (s[j]==s[i]&&j<s.length()) j++;
                                ~^~~~~~~~~~~