/in/foo.cc: In function 'int main()':
/in/foo.cc:12:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<s.length(); i++) {
               ~^~~~~~~~~~~
/in/foo.cc:28:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  } else if(pos+k>=s.length()-1) {
            ~~~~~^~~~~~~~~~~~~~
/in/foo.cc:30:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(pos==s.length()) {
      ~~~^~~~~~~~~~~~
/in/foo.cc:43:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  } else if(pos+k<s.length()-1) {
            ~~~~~^~~~~~~~~~~~~