/in/foo.cc: In function 'int main()':
/in/foo.cc:10:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<s.length();i++)
                ^
/in/foo.cc:15:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(sum==s.length())
         ^