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.List;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.Reader;
import java.io.InputStreamReader;
import java.io.InputStream;
import java.util.ArrayList;

/**
 * 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;
        MyInput in = new MyInput(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        CCrazyDiamond solver = new CCrazyDiamond();
        solver.solve(1, in, out);
        out.close();
    }

    static class CCrazyDiamond {
        List<String> ans = new ArrayList<>();

        public void solve(int testNumber, MyInput in, PrintWriter out) {
            int n = in.nextInt();
            int[] ps = in.nextIntArray(n);
            int[] pos = new int[n];
            for (int i = 0; i < n; i++) {
                pos[--ps[i]] = i;
            }
            for (int i = n / 2; i < n - 1; i++) {
                if (2 * Math.abs(pos[i] - i) >= n) {
                    swap(ps, pos, pos[i], i);
                } else if (2 * Math.abs(pos[i] - 0) >= n) {
                    swap(ps, pos, 0, pos[i]);
                    swap(ps, pos, 0, i);
                } else {
                    swap(ps, pos, n - 1, pos[i]);
                    swap(ps, pos, 0, n - 1);
                    swap(ps, pos, 0, i);
                }
            }
            for (int i = 1; i < n / 2; i++) {
                if (2 * Math.abs(pos[i] - i) >= n) {
                    swap(ps, pos, pos[i], i);
                } else if (2 * Math.abs(pos[i] - (n - 1)) >= n) {
                    swap(ps, pos, n - 1, pos[i]);
                    swap(ps, pos, n - 1, i);
                } else {
                    swap(ps, pos, 0, pos[i]);
                    swap(ps, pos, 0, n - 1);
                    swap(ps, pos, n - 1, i);
                }
            }
            if (ps[0] != 0) {
                swap(ps, pos, 0, n - 1);
            }
            out.println(ans.size());
            for (String s : ans) {
                out.println(s);
            }
        }

        void swap(int[] ps, int[] pos, int i, int j) {
            int a = ps[i], b = ps[j];
            swap(ps, i, j);
            swap(pos, a, b);
            ans.add((i + 1) + " " + (j + 1));
        }

        static void swap(int[] xs, int i, int j) {
            int t = xs[i];
            xs[i] = xs[j];
            xs[j] = t;
        }

    }

    static class MyInput {
        private final BufferedReader in;
        private static int pos;
        private static int readLen;
        private static final char[] buffer = new char[1024 * 8];
        private static char[] str = new char[500 * 8 * 2];
        private static boolean[] isDigit = new boolean[256];
        private static boolean[] isSpace = new boolean[256];
        private static boolean[] isLineSep = new boolean[256];

        static {
            for (int i = 0; i < 10; i++) {
                isDigit['0' + i] = true;
            }
            isDigit['-'] = true;
            isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true;
            isLineSep['\r'] = isLineSep['\n'] = true;
        }

        public MyInput(InputStream is) {
            in = new BufferedReader(new InputStreamReader(is));
        }

        public int read() {
            if (pos >= readLen) {
                pos = 0;
                try {
                    readLen = in.read(buffer);
                } catch (IOException e) {
                    throw new RuntimeException();
                }
                if (readLen <= 0) {
                    throw new MyInput.EndOfFileRuntimeException();
                }
            }
            return buffer[pos++];
        }

        public int nextInt() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            int i = 0;
            int ret = 0;
            if (str[0] == '-') {
                i = 1;
            }
            for (; i < len; i++) ret = ret * 10 + str[i] - '0';
            if (str[0] == '-') {
                ret = -ret;
            }
            return ret;
        }

        public char nextChar() {
            while (true) {
                final int c = read();
                if (!isSpace[c]) {
                    return (char) c;
                }
            }
        }

        int reads(int len, boolean[] accept) {
            try {
                while (true) {
                    final int c = read();
                    if (accept[c]) {
                        break;
                    }
                    if (str.length == len) {
                        char[] rep = new char[str.length * 3 / 2];
                        System.arraycopy(str, 0, rep, 0, str.length);
                        str = rep;
                    }
                    str[len++] = (char) c;
                }
            } catch (MyInput.EndOfFileRuntimeException e) {
            }
            return len;
        }

        public int[] nextIntArray(final int n) {
            final int[] res = new int[n];
            for (int i = 0; i < n; i++) {
                res[i] = nextInt();
            }
            return res;
        }

        static class EndOfFileRuntimeException extends RuntimeException {
        }

    }
}