/in/foo.cc: In function 'int main()':
/in/foo.cc:11:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<s.length(); i++)
               ~^~~~~~~~~~~
/in/foo.cc:17:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int j=1; j<c.length(); j++)
                 ~^~~~~~~~~~~
/in/foo.cc:24:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(flag==c.length())
      ~~~~^~~~~~~~~~~~