As the method of exclusively allocating values, for example, there is a method by which some integers in a range of 0 to N(1)???N(2)??? . . . ???N(M)???1 are used as values of the user IDs, and a remainder obtained by dividing a target user ID by N(i) with respect to each of the M integers A(i) is determined as a value of A(i) corresponding to the user ID. In this embodiment, it is desirable that