... either of these is the result of deleting the letters {3, 4, ,k− 4} from w,thenw must be either a word starting within the 0v1,k−4block and ending at the end of xkor a word starting at the ... in w3,allofw2is contained in hk−1,sothereisapairof2’s in wk−1. The half-way point for s3, however, is in w1, so all four appearances of 2 areto the right of the half-way point for ... sk−1 and one would have to be in the left. Since both would haveto be in the same wi,bothmustbeinw2, but then the first, being in w2andonthelefthalf of sk−1, would be in hk−1, and there...