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.*;
import java.util.*;
import java.util.stream.*;

public class ProblemC {
    private static boolean debug = false;

    private static int N;
    private static int[] A;

    private static void solveProblem(InputStream instr) throws Exception {
        InputReader sc = new InputReader(instr);
        int testCount = 1;
        if (debug) {
            testCount = sc.nextInt();
        }

        for (int t = 1; t <= testCount; t++) {
            printDebug("------ " + t + " ------");
            N = sc.nextInt();
            A = readInts(sc, N);
            Object result = solveTestCase();
            System.out.println(result);
        }
    }

    private static Object solveTestCase() {
        int mid = N / 2;
        int indexes[] = new int[N + 1];
        for (int i = 0; i < N; i++) {
            indexes[A[i]] = i;
        }
        List<String> steps = new ArrayList<>();
        for (int i = 0; i < N; i++) {
            int num = i + 1;
            int numIndex = indexes[num];
            if (numIndex == i) {
                continue;
            }
            if (i < mid) {
                if (numIndex >= i + mid) {
                    String step1 = swap(i, numIndex, indexes);
                    steps.add(step1);
                } else if (numIndex < mid) {
                    String step1 = swap(numIndex, numIndex + mid, indexes);
                    String step2 = swap(i, numIndex + mid, indexes);
                    steps.add(step1);
                    steps.add(step2);
                } else {
                    String step1 = swap(numIndex - mid, numIndex, indexes);
                    String step2 = swap(numIndex - mid, i + mid, indexes);
                    String step3 = swap(numIndex - mid, numIndex, indexes);
                    String step4 = swap(i, i + mid, indexes);
                    steps.add(step1);
                    steps.add(step2);
                    steps.add(step3);
                    steps.add(step4);
                }
            } else {
                int first = i - mid;
                String step1 = swap(first, numIndex, indexes);
                String step2 = swap(first, i, indexes);
                String step3 = swap(first, numIndex, indexes);
                steps.add(step1);
                steps.add(step2);
                steps.add(step3);
            }
        }
        for (int i = 0; i < N; i++) {
            if (A[i] != i + 1) {
                throw new RuntimeException("Wrong answer");
            }
        }
        return steps.size() + "\n" + joinValues(steps, "\n");
    }

    private static String swap(int index1, int index2, int[] indexes) {
        indexes[A[index1]] = index2;
        indexes[A[index2]] = index1;
        int temp = A[index1];
        A[index1] = A[index2];
        A[index2] = temp;
        return (index1 + 1) + " " + (index2 + 1);
    }

    public static void shuffle(int[] array) {
        Random rand = new Random();
        for (int i = 0; i < array.length; i++) {
            int x = rand.nextInt(array.length - i);
            int idx = x + i;
            int tmp = array[idx];
            array[idx] = array[i];
            array[i] = tmp;
        }
    }

    private static int[] readInts(InputReader sc, int N) throws Exception {
        int[] arr = new int[N];
        for (int i = 0; i < N; i++) {
            arr[i] = sc.nextInt();
        }
        return arr;
    }

    private static String joinValues(List<? extends Object> list, String delim) {
        return list.stream().map(Object::toString).collect(Collectors.joining(delim));
    }

    private static String joinValues(int[] arr, String delim) {
        List<Object> list = new ArrayList<>();
        for (Object value : arr) {
            list.add(value);
        }
        return list.stream().map(Object::toString).collect(Collectors.joining(delim));
    }

    public static void printDebug(Object str) {
        if (debug) {
            System.out.println("DEBUG: " + str);
        }
    }

    private static final class InputReader {
        private final InputStream stream;
        private final byte[] buf = new byte[1024];
        private int curChar;
        private int Chars;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        private int read() throws Exception {
            if (curChar >= Chars) {
                curChar = 0;
                Chars = stream.read(buf);
                if (Chars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }

        public final int nextInt() throws Exception {
            return (int)nextLong();
        }

        public final long nextLong() throws Exception {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
                if (c == -1)
                    throw new IOException();
            }
            boolean negative = false;
            if (c == '-') {
                negative = true;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += (c - '0');
                c = read();
            } while (!isSpaceChar(c));
            return negative ? (-res) : (res);
        }

        public final int[] nextIntBrray(int size) throws Exception {
            int[] arr = new int[size];
            for (int i = 0; i < size; i++)
                arr[i] = nextInt();
            return arr;
        }

        public final String next() throws Exception {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.append((char)c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public final String nextLine() throws Exception {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.append((char)c);
                c = read();
            } while (c != '\n' && c != -1);
            return res.toString();
        }

        private boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
    }

    public static void main(String[] args) throws Exception {
        long currTime = System.currentTimeMillis();
        try {
            if (new File("input.in").exists()) {
                debug = true;
            }
        } catch (Throwable ex) {

        }
        if (debug) {
            solveProblem(new FileInputStream(new File("input.in")));
            System.out.println("Time: " + (System.currentTimeMillis() - currTime));
        } else {
            solveProblem(System.in);
        }
    }

}