/in/foo.cc: In function 'int main()':
/in/foo.cc:8:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<s1.size()-1;i++)cout<<s1[i];
              ~^~~~~~~~~~~~
/in/foo.cc:9:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=1;i<s2.size();i++)cout<<s2[i];
              ~^~~~~~~~~~