All words in the right span must be rechecked, because aligning them to the inserted token at q + 1 may yield a better translation score.
this update requires ) removes the first token of the left span with index p. After removing the token, new alignments must be found for all tokens that were aligned to p. the number of operations for this update is K × (q − p + 1), where K is the number of words that were originally aligned to p. In the best case, no words are aligned to the token in p, so nothing needs to be done.