Problem: You 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 ⋅ |i - j| ≥ 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 ⋅ n operations. One can show that it is always possible to do that.

Input

The first line contains a single integer n (2 ≤ n ≤ 3 ⋅ 10^5, n is even) — the length of the permutation. 

The second line contains n distinct integers p_1, p_2, …, p_n (1 ≤ p_i ≤ n) — the given permutation.

Output

On the first line print m (0 ≤ m ≤ 5 ⋅ n) — the number of swaps to perform.

Each of the following m lines should contain integers a_i, b_i (1 ≤ a_i, b_i ≤ n, |a_i - b_i| ≥ 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.

Examples

Input


2
2 1


Output


1
1 2

Input


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

Note

In 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].

Solution (in PYTHON3):

Solution:
import sys,math

def read_int():
	return int(sys.stdin.readline().strip())

def read_int_list():
	return list(map(int,sys.stdin.readline().strip().split()))

def read_string():
	return sys.stdin.readline().strip()

def read_string_list(delim=" "):
	return sys.stdin.readline().strip().split(delim)


###### Author : Samir Vyas #######
###### Write Code Below    #######


def swap(this_index, true_index):
	global pos, arr, outs
	pos[arr[this_index]] = true_index
	pos[arr[true_index]] = this_index
	arr[this_index], arr[true_index] = arr[true_index], arr[this_index]

	outs.append((this_index+1, true_index+1))

	if abs(true_index - this_index) < limit:
		print("fuck!")

	# print(arr)


n = read_int()
arr = read_int_list()
outs = []
# print(arr)
limit = n//2

pos = {}
for i in range(n):
	pos[arr[i]] = i

i = 0
while i<n:
	#not in place
	if arr[i] != i+1:
		#find element
		true_index = pos[i+1]
		this_index = i

		#if allowed
		if abs(true_index - this_index) >= limit:
			swap(this_index, true_index)

		#else:
		else:
			#both in left half
			if this_index < n//2 and true_index < n//2:
				sentinal = n-1
				#swap true with sentinal -> this with sentinal ->  sentinal with true
				swap(true_index, sentinal); swap(this_index, sentinal); swap(sentinal, true_index) 

			#both in second half
			elif this_index >= n//2 and true_index >= n//2:
				sentinal = 0
				#swap true with sentinal -> this with sentinal ->  sentinal with true
				swap(true_index, sentinal); swap(this_index, sentinal); swap(sentinal, true_index) 

			#both in different halves
			else:
				sentinal_1, sentinal_2 = 0,n-1
				first,second = min(this_index, true_index), max(this_index, true_index)
				swap(first, sentinal_2); swap(second, sentinal_1); swap(sentinal_1, sentinal_2); swap(sentinal_1, second); swap(sentinal_2, first)


	i += 1


print(len(outs))
for t in outs:
	print(t[0], t[1])