e.g. ‘a’ vs. ‘s’
	• “zasha” vs. “ashes”.  2 possibilities for last letters: – (1) match ‘a’ with ‘_’: • best_alignment(“zash”,”ashes”)+1 – (2) match ‘s’ with ‘_’: • best_alignment(“zasha”,”ashe”)+1 • à best_alignment(“zasha”,”ashes”) =min(best_alignment(“zash”,”ashes”)+1,          best_alignment(“zasha”,”ashe”)+1)