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 PYTHON):

Solution:
from sys import stdout

n = input()
p = map(int, raw_input().strip().split())

swaps = []

# First step is to make the halves valid
# i.e. 1st half must contain only numbers 1 to n / 2
# and the other half contains the rest.

# How to do it?

# Determine the outsiders in first half
# swap them with the outsiders in second half
# using the first and last elements as pivots

mid = n / 2

left = []
right = []

for i in xrange(mid):
    if p[i] > mid:
        left.append(i)

for i in xrange(mid, n):
    if p[i] <= mid:
        right.append(i)

# If last element is an outsider, then
# swap it freely with some outsider in first half.
# Do the same for first element.
# Then use the new first and last elements as pivots.

# This takes less than (3/2)*n swaps.

if len(right) != 0:
    if right[-1] == n - 1:
        i, j = left.pop(), right.pop()
        
        p[i], p[j] = p[j], p[i]
        swaps.append(' '.join(map(str, [i + 1, j + 1])))
        
    if len(left) and left[0] == 0:
        sz = len(left)
        left[0], left[sz - 1] = left[sz - 1], left[0]
        right[0], right[sz - 1] = right[sz - 1], right[0]
        
        i, j = left.pop(), right.pop()

        p[i], p[j] = p[j], p[i]
        swaps.append(' '.join(map(str, [i + 1, j + 1])))

    while len(right):
        first = 0
        last = n - 1
        i, j = left.pop(), right.pop()

        if abs(i - j) >= mid:
            p[i], p[j] = p[j], p[i]
            swaps.append(' '.join(map(str, [i + 1, j + 1])))
            continue

        p[first], p[last] = p[last], p[first]
        swaps.append(' '.join(map(str, [first + 1, last + 1])))

        p[first], p[j] = p[j], p[first]
        swaps.append(' '.join(map(str, [first + 1, j + 1])))

        p[i], p[last] = p[last], p[i]
        swaps.append(' '.join(map(str, [i + 1, last + 1])))

# Now the elements are in their correct halves.
# Now for swapping inside a half, we can use the extreme
# point of the other half as a pivot.

# This again takes (3/2)*n swaps for each half in worst case.
# So total of 3*n swaps for full array.

# find the current indices
pos = [0] * n
for i in xrange(n): pos[p[i] - 1] = i

first, last = 0, n - 1
    
# now do swapping
# for 1st half
for i in xrange(mid):
    if p[i] != i + 1:
        # to swap with
        j = pos[i]

        # this is the result after swap
        pos[p[i] - 1] = j
        pos[i] = i

        # the swaps
        p[i], p[last] = p[last], p[i]
        swaps.append(' '.join(map(str, [i + 1, last + 1])))

        p[j], p[last] = p[last], p[j]
        swaps.append(' '.join(map(str, [j + 1, last + 1])))

        p[i], p[last] = p[last], p[i]
        swaps.append(' '.join(map(str, [i + 1, last + 1])))

# for second half
for i in xrange(mid, n):
    if p[i] != i + 1:
        # to swap with
        j = pos[i]

        # this is the result after swap
        pos[p[i] - 1] = j
        pos[i] = i

        # the swaps
        p[first], p[i] = p[i], p[first]
        swaps.append(' '.join(map(str, [first + 1, i + 1])))

        p[first], p[j] = p[j], p[first]
        swaps.append(' '.join(map(str, [first + 1, j + 1])))

        p[first], p[i] = p[i], p[first]
        swaps.append(' '.join(map(str, [first + 1, i + 1])))

# We are done now.
# Grand total <= (3/2)*n + 3*n = 4.5*n < 5*n.
# So this should be good.

print len(swaps)
stdout.write("\n".join(swaps))