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

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