You have an array a[1], a[2], ..., a[n], containing distinct integers from 1 to n. Your task is to sort this array in increasing order with the following operation (you may need to apply it multiple times): You do not need to minimize the number of used operations. However, you need to make sure that there are at most 5n operations. The first line contains integer n (1 ≤ n ≤ 105). The next line contains n distinct integers a[1], a[2], ..., a[n] (1 ≤ a[i] ≤ n). In the first line, print integer k (0 ≤ k ≤ 5n) -- the number of used operations. Next, print the operations. Each operation must be printed as "i j" (1 ≤ i < j ≤ n; (j - i + 1) is a prime). If there are multiple answers, you can print any of them.