/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<a.size();i++) a[i]=a[i+1];
              ~^~~~~~~~~
/in/foo.cc:10:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a.size();i++) cout<<a[i];
              ~^~~~~~~~~