/in/foo.cc: In function 'bool cmp()':
/in/foo.cc:8:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int j=0;j<s.length();j++,i++){
              ~^~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:18:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while(i<str.length()){
        ~^~~~~~~~~~~~~