C. Crazy Diamondtime limit per test3 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard outputYou are given a permutation p of integers from 1 to n, where n is an even number. Your goal is to sort the permutation. To do so, you can perform zero or more operations of the following type:   take two indices i and j such that 2 \cdot |i - j| \geq n and swap p_i and p_j. There is no need to minimize the number of operations, however you should use no more than 5 \cdot n operations. One can show that it is always possible to do that.InputThe first line contains a single integer n (2 \leq n \leq 3 \cdot 10^5, n is even) — the length of the permutation. The second line contains n distinct integers p_1, p_2, \ldots, p_n (1 \le p_i \le n) — the given permutation.OutputOn the first line print m (0 \le m \le 5 \cdot n) — the number of swaps to perform.Each of the following m lines should contain integers a_i, b_i (1 \le a_i, b_i \le n, |a_i - b_i| \ge \frac{n}{2}) — the indices that should be swapped in the corresponding swap.Note that there is no need to minimize the number of operations. We can show that an answer always exists.ExamplesInput
2
2 1
Output
1
1 2Input
4
3 4 1 2
Output
4
1 4
1 4
1 3
2 4
Input
6
2 5 3 1 4 6
Output
3
1 5
2 5
1 4
NoteIn the first example, when one swap elements on positions 1 and 2, the array becomes sorted.In the second example, pay attention that there is no need to minimize number of swaps.In the third example, after swapping elements on positions 1 and 5 the array becomes: [4, 5, 3, 1, 2, 6]. After swapping elements on positions 2 and 5 the array becomes [4, 2, 3, 1, 5, 6] and finally after swapping elements on positions 1 and 4 the array becomes sorted: [1, 2, 3, 4, 5, 6].
2
2 1

1 1 2
['constructive algorithms', 'sortings', '*1700']