/in/foo.cc: In function 'int main()':
/in/foo.cc:18:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(j = 0; j < s.size() && s[j] == '0'; j++)
              ~~^~~~~~~~~~
/in/foo.cc:20:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(j == s.size())
      ~~^~~~~~~~~~~
/in/foo.cc:24:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(; j < s.size(); j++)
          ~~^~~~~~~~~~