private static Integer getNextInstanceOfNegation(LinkedList<Token> tokens, int startingAtIndex) {
		
		for(int i=startingAtIndex; i<tokens.size();i++) {
			
			Token t = tokens.get(i);
			if(t.getUnderlyingObject()==Operation.NEGATION) {
				return i;
			}
		}
		return null;
	}