Proof. For insert in ROTATED LIBRARY SORT, hard exchanges on Jk are unavoidable initially. However, the larger the is, fewer hard exchanges on Jr−1 will be required at the end. Therefore, the worst case sceanrio happens when insertion occurs at Jk where k = r/2. Each in sertion consists of a binary search with O(lgr)operations. The first (f(k)−1) insertions include a hard exchange, that costs worst case O(f(k)) operations, because of the empty gaps. The (f(k))-th insertion will incur the initial hard exchange plus a soft exchange on Jk+1 that costs O(f(k)) operations.