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 os
import heapq
import sys
import math
import bisect
import operator
from collections import defaultdict
from io import BytesIO, IOBase
def gcd(a,b):
    if b==0:

        return a
    else:
        return gcd(b,a%b)
def power(x, p,m):
    res = 1
    while p:
        if p & 1:
            res = (res * x) % m
        x = (x * x) % m
        p >>= 1
    return res
def inar():
    return [int(k) for k in input().split()]


# def bubbleSort(arr,b):
#     n = len(arr)
#     for i in range(n):
#         for j in range(0, n - i - 1):
#             if arr[j] > arr[j + 1] and b[j]!=b[j+1]:
#                 arr[j], arr[j + 1] = arr[j + 1], arr[j]
#                 b[j],b[j+1]=b[j+1],b[j]
def lcm(num1,num2):
    return (num1*num2)//gcd(num1,num2)
def binaryToDecimal(n):
    return int(n,2)

def main():
    n = int(input())
    arr = [int(el) for el in input().split()]
    i = 0
    res = []
    while i < n:
        # print(i)
        # print(*arr)
        if arr[i] - 1 == i:
            i += 1
        else:
            pos2 = arr[i] - 1
            if abs(pos2 - i) >= (n // 2):
                res.append([min(i + 1, pos2 + 1), max(i + 1, pos2 + 1)])
                temp = arr[i]
                arr[i] = arr[pos2]
                arr[pos2] = temp
            elif i < (n // 2) and pos2 < (n // 2):
                res.append([i + 1, n])
                res.append([pos2 + 1, n])
                res.append([i + 1, n])
                temp = arr[i]
                arr[i] = arr[pos2]
                arr[pos2] = temp
            elif i < n // 2 <= pos2:
                res.append([i + 1, n])
                res.append([1, pos2 + 1])
                res.append([1, n])
                res.append([1, pos2 + 1])
                res.append([i + 1, n])
                temp = arr[i]
                arr[i] = arr[pos2]
                arr[pos2] = temp
            else:
                res.append([1, i + 1])
                res.append([1, pos2 + 1])
                res.append([1, i + 1])
                temp = arr[i]
                arr[i] = arr[pos2]
                arr[pos2] = temp
    print(len(res))
    for i in range(len(res)):
        print(*res[i])







BUFSIZE = 8192


class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")


sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda: sys.stdin.readline().rstrip("\r\n")

if __name__ == "__main__":
    main()