Before revision:  For this }  , Alice and Bob have to achieve effective communication within the locker room.
After revision:  For this } We want to efficiently find a specific object in a large unstructured set, which we model by a random n-permutation, and we have to do it by revealing just a single element. Clearly, without any help this task is hopeless and the best one can do is select the element at random, and achieve the success probability \frac{1 , Alice and Bob have to achieve effective communication within the locker room.