/in/foo.cc: In function 'int main()':
/in/foo.cc:71:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<s.size();i++) {
              ~^~~~~~~~~
/in/foo.cc:73:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   ans+=Dis(s[i],s[(i+1==s.size()?0:i+1)]);
                    ~~~^~~~~~~~~~