/in/foo.cc: In function 'int main()':
/in/foo.cc:12:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<s2.length();i++){
                      ^
/in/foo.cc:18:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if(sum<s2.length()/2){
                   ^
/in/foo.cc:26:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if(sum<=s2.length()/2){
                   ^