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:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;

public class SolutionC {

    public static void main(String[] args) throws IOException {
        Reader reader = new Reader();
        int n = reader.readIntValue();
        int[] p = reader.readIntNumbers();
        int[] numberPositions = new int[p.length + 1];
        for (int i = 0; i < p.length; i++) {
            int value = p[i];
            numberPositions[value] = i + 1;
        }

        StringBuilder output = new StringBuilder("");
        int swapsNum = 0;
        for (int num = 1; num < numberPositions.length; num++) {
            int pos = numberPositions[num];
            if (Math.abs(pos - num) * 2 >= n) {
                swap(p, numberPositions, num, pos, output);
                swapsNum++;
            } else {
                if (num <= n / 2 && pos > n / 2) {
                    swap(p, numberPositions, pos, 1, output);
                    swap(p, numberPositions, 1, n, output);
                    swap(p, numberPositions, num, n, output);
                    swapsNum += 3;
                } else if (num <= n / 2 && pos <= n / 2) {
                    swap(p, numberPositions, pos, n, output);
                    swap(p, numberPositions, num, n, output);
                    swapsNum += 2;
                } else if (num > n / 2 && pos > n / 2) {
                    swap(p, numberPositions, pos, 1, output);
                    swap(p, numberPositions, num, 1, output);
                    swapsNum += 2;
                } else if (num > n / 2 && pos <= n / 2) {
                    swap(p, numberPositions, pos, n, output);
                    swap(p, numberPositions, pos, 1, output);
                    swap(p, numberPositions, num, 1, output);
                    swapsNum += 3;
                }


            }

        }

//        for(int i = 0; i < n; i++) {
//            System.out.print(p[i] + " ");
//        }
        System.out.println(swapsNum);
        System.out.print(output.toString());


    }

    private static void swap(int[] p, int[] numberPositions, int i, int j, StringBuilder output) {
        int tempI = p[i - 1];
        int tempJ = p[j - 1];
        p[i - 1] = tempJ;
        p[j - 1] = tempI;

        numberPositions[tempI] = j;
        numberPositions[tempJ] = i;
        output.append(i).append(" ").append(j).append("\n");
    }

}

class Reader {

    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));

    public StringTokenizer getStringTokenizer() throws IOException {
        String line = bufferedReader.readLine().replaceAll("\\s+$", "");
        return new StringTokenizer(line, " ");
    }

    public int getNextInt(StringTokenizer stringTokenizer) {
        while (stringTokenizer.hasMoreTokens()) {
            return Integer.parseInt(stringTokenizer.nextToken());
        }
        throw new RuntimeException("no more tokens in string");
    }

    public long getNextLong(StringTokenizer stringTokenizer) {
        while (stringTokenizer.hasMoreTokens()) {
            return Long.parseLong(stringTokenizer.nextToken());
        }
        throw new RuntimeException("no more tokens in string");
    }

    public String getNextString(StringTokenizer stringTokenizer) {
        while (stringTokenizer.hasMoreTokens()) {
            return stringTokenizer.nextToken();
        }
        throw new RuntimeException("no more tokens in string");
    }

    public String readStringValue() throws IOException {
        return bufferedReader.readLine().replaceAll("\\s+$", "");
    }

    public int readIntValue() throws IOException {
        String line = bufferedReader.readLine().replaceAll("\\s+$", "");
        int parsedToInt = Integer.parseInt(line);
        return parsedToInt;
    }

    public int[] readIntNumbers() throws IOException {
        String[] line = bufferedReader.readLine().replaceAll("\\s+$", "").split(" ");
        int[] parsedToInt = Arrays.stream(line).mapToInt(Integer::parseInt).toArray();
        return parsedToInt;
    }

    public long readLongValue() throws IOException {
        String line = bufferedReader.readLine().replaceAll("\\s+$", "");
        long parsedToLong = Long.parseLong(line);
        return parsedToLong;
    }

    public long[] readLongNumbers() throws IOException {
        String[] line = bufferedReader.readLine().replaceAll("\\s+$", "").split(" ");
        long[] parsedToLong = Arrays.stream(line).mapToLong(Long::parseLong).toArray();
        return parsedToLong;
    }

}