code: private String w(Sentence sent, int pos, int i){
  		String cp = "w:" + Integer.toString(i) + ":"; 
  		//if (pos + i == -1)
  		//	cp += "BS";
  		//else if (pos + i == sent.size())
  		//	cp += "ES";
  		if (0 <= (pos + i) && (pos + i) < sent.size())
  			cp += sent.getWordAt(pos + i);
  		else cp="";
  		
  		return cp;
  	}
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