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 JAVA):

Solution:
/**
 * ******* Created on 21/9/19 8:55 AM*******
 */

import java.io.*;
import java.util.*;

public class C1148 implements Runnable{
    ArrayList<Integer>ans1;
    ArrayList<Integer>ans2;
    int n;
    int[] arr = new int[300005];
    int[] p = new int[300005];
    public static void main(String[] args) throws IOException {
        new C1148().run();
    }

    private void solve() throws IOException {
        ans1 = new ArrayList<>();
        ans2 = new ArrayList<>();
        try (Input input = new StandardInput(); PrintWriter writer = new PrintWriter(System.out)) {
            n =  input.nextInt();
            for(int i=1;i<=n;i++){
                arr[i] = input.nextInt();
                p[arr[i]]=i;
            }

            for(int i=1;i<=n;i++){
                int ind = p[i];
                if(arr[i]!=i){
                    pSwap(ind,i);
                }

            }
            writer.println(ans1.size());
            for(int i=0;i<ans1.size();i++)
                writer.println(ans1.get(i)+" "+ans2.get(i));

        }
    }

    private  void pSwap(int ind1, int ind2) {
        if(ind1 > ind2){
            int temp =ind1;
            ind1 = ind2;
            ind2 = temp;
        }
        if( (ind2-ind1) *2 >=n){
            swap(ind1, ind2);
        }
        else if(ind2 <= n/2){
            swap(ind1, n);
            swap(ind2,n);
            swap(ind1,n);
        }else if(ind1 > n/2){
            swap(ind1,1);
            swap(ind2,1);
            swap(ind1,1);
        }
        else{
            swap(ind1,n);
            swap(ind2,1);
            swap(1,n);
            swap(ind1,n);
            swap(ind2,1);
        }
    }

    private  void swap(int ind1, int ind2) {
        int temp = arr[ind1];
        arr[ind1]= arr[ind2];
        arr[ind2] = temp;
        p[arr[ind1]]=ind1;
        p[arr[ind2]]=ind2;
        ans1.add(ind1);
        ans2.add(ind2);
    }

    @Override
    public void run() {
        try{
            solve();
        }catch (Exception e){
            e.printStackTrace();
        }

    }

    interface Input extends Closeable {
        String next() throws IOException;

        default int nextInt() throws IOException {
            return Integer.parseInt(next());
        }

        default long nextLong() throws IOException {
            return Long.parseLong(next());
        }

        default double nextDouble() throws IOException {
            return Double.parseDouble(next());
        }

        default int[] readIntArray() throws IOException {
            return readIntArray(nextInt());
        }

        default int[] readIntArray(int size) throws IOException {
            int[] array = new int[size];
            for (int i = 0; i < array.length; i++) {
                array[i] = nextInt();
            }
            return array;
        }

        default long[] readLongArray(int size) throws IOException {
            long[] array = new long[size];
            for (int i = 0; i < array.length; i++) {
                array[i] = nextLong();
            }
            return array;
        }
    }

    private static class StandardInput implements Input {
        private final BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        private StringTokenizer stringTokenizer;

        @Override
        public void close() throws IOException {
            reader.close();
        }

        @Override
        public String next() throws IOException {
            if (stringTokenizer == null || !stringTokenizer.hasMoreTokens()) {
                stringTokenizer = new StringTokenizer(reader.readLine());
            }
            return stringTokenizer.nextToken();
        }
    }
}