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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastScanner in = new FastScanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskC {
        int n;
        int[] a;
        int[] where;
        int[] ansA;
        int[] ansB;
        int k;

        public void solve(int testNumber, FastScanner in, PrintWriter out) {
            n = in.nextInt();
            a = new int[n];
            where = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = in.nextInt() - 1;
                where[a[i]] = i;
            }

            ansA = new int[5 * n];
            ansB = new int[5 * n];
            int[] far = {0, 1, n - 1, n - 2};
            for (int step = 0; step < n; step++) {
                int i = where[step];
                int j = step;
                if (i == j) {
                    continue;
                }
                if (2 * Math.abs(i - j) >= n) {
                    swap(i, j);
                    continue;
                }

                boolean hi = i < n / 2;
                boolean hj = j < n / 2;
                if (hi == hj) {
                    int x = -1;
                    for (int cand : far) {
                        if (2 * Math.abs(i - cand) >= n && 2 * Math.abs(j - cand) >= n && cand != i && cand != j) {
                            x = cand;
                            break;
                        }
                    }
                    swap(i, x);
                    swap(j, x);
                    swap(i, x);
                    if (x < 0) {
                        throw new AssertionError();
                    }
                    continue;
                }
                if (hi != hj) {
                    int x = -1;
                    int y = -1;
                    for (int cand : far) {
                        if (2 * Math.abs(i - cand) >= n && cand != i && cand != j) {
                            x = cand;
                            break;
                        }
                    }
                    for (int cand : far) {
                        if (2 * Math.abs(j - cand) >= n && 2 * Math.abs(x - cand) >= n && cand != i && cand != j && cand != x) {
                            y = cand;
                            break;
                        }
                    }
                    if (x < 0 || y < 0) {
                        throw new AssertionError();
                    }
                    swap(i, x);
                    swap(j, y);
                    swap(x, y);
                    swap(i, x);
                    swap(j, y);
                    continue;
                }
            }

            for (int i = 0; i < n; i++) {
                if (a[i] != i) {
                    throw new AssertionError();
                }
            }
            out.println(k);
            for (int i = 0; i < k; i++) {
                out.println((ansA[i] + 1) + " " + (ansB[i] + 1));
            }
        }

        private void swap(int i, int j) {
            if (2 * Math.abs(i - j) < n) {
                throw new AssertionError();
            }
            ansA[k] = i;
            ansB[k] = j;
            ++k;

            int ai = a[i];
            int aj = a[j];
            a[i] = aj;
            a[j] = ai;
            where[a[i]] = i;
            where[a[j]] = j;
        }

    }

    static class FastScanner {
        private BufferedReader in;
        private StringTokenizer st;

        public FastScanner(InputStream stream) {
            in = new BufferedReader(new InputStreamReader(stream));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
}