foo.cc: In function 'int main()':
foo.cc:9:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if(index>=str.size()) {
     ~~~~~^~~~~~~~~~~~
foo.cc:13:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(i=index;i!=str.size();i++)
              ~^~~~~~~~~~~~

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