/in/foo.cc: In function 'int main()':
/in/foo.cc:11:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(si<=s.length())
      ~~^~~~~~~~~~~~
/in/foo.cc:20:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int i=0;i<s.length();i++)
                ~^~~~~~~~~~~
/in/foo.cc:26:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(len<s.length())
      ~~~^~~~~~~~~~~
/in/foo.cc:28:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int i=len;i<s.length();i++)
                  ~^~~~~~~~~~~