foo.cc: In function 'int main()':
foo.cc:9:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if(now5==str.size()-1) {
     ~~~~^~~~~~~~~~~~~~
foo.cc:13:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(i=now5;i!=str.size();i++)
             ~^~~~~~~~~~~~
foo.cc:8:35: warning: unused variable 'j' [-Wunused-variable]
  int last5=0,now5=str.find('5'),i,j;
                                   ^

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