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.OutputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.FileNotFoundException;
import java.io.File;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;
import java.io.Writer;
import java.io.BufferedReader;
import java.io.FileReader;
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;
    InputReader in = new InputReader(inputStream);
    OutputWriter out = new OutputWriter(outputStream);
    TaskS solver = new TaskS();
    solver.solve(1, in, out);
    out.close();
  }

  static class TaskS extends ChelperSolution {
    private int[] p;
    private int[] where;
    private List<String> swaps;
    private int n;

    public void solve(int testNumber, InputReader in, OutputWriter out) {
      super.solve(testNumber, in, out);
    }

    void swap(int i, int j) {
      if (!isOk(i, j)) {
        throw new RuntimeException();
      }

      swaps.add((i + 1) + " " + (j + 1));

      int t = p[i];
      p[i] = p[j];
      p[j] = t;

      where[p[i]] = i;
      where[p[j]] = j;
    }

    private boolean isOk(int i, int j) {
      return Math.abs(i - j) * 2 >= n;
    }

    public void solve(int testNumber) {
      n = in.nextInt();

      swaps = new ArrayList<>();

      p = in.nextIntArray(n);
      for (int i = 0; i < n; i++) {
        p[i]--;
      }

      where = new int[n];

      for (int i = 0; i < n; i++) {
        where[p[i]] = i;
      }

      for (int fromCenter = 0; fromCenter < n / 2; fromCenter++) {
        handle(n / 2 - 1 - fromCenter);
        handle(n / 2 + fromCenter);
      }

      out.println(swaps.size());
      for (String s : swaps) {
        out.println(s);
      }

      debug.println(Arrays.toString(p));
    }

    int closestEnd(int pos) {
      return pos < n / 2 ? n - 1 : 0;
    }

    private void handle(int pos) {
      if (p[pos] == pos) {
        return;
      }

      int x = where[pos];

      if (isOk(pos, x)) {
        swap(pos, x);
        return;
      }

      swap(x, closestEnd(x));
      x = closestEnd(x);

      if (isOk(pos, x)) {
        swap(pos, x);
        return;
      }

      swap(x, closestEnd(x));
      x = closestEnd(x);

      if (isOk(pos, x)) {
        swap(pos, x);
        return;
      }

      throw new RuntimeException();
    }

  }

  static interface ChelperCallable {
  }

  static abstract class ChelperSolution implements ChelperCallable {
    public static final String LOCAL_FILE = "chelper.properties";
    public static final String SAVE_RESULT_FILE = "last_test_output.txt";
    protected final boolean local = new File(LOCAL_FILE).exists();
    protected boolean firstTest = true;
    protected InputReader in;
    protected OutputWriter out;
    protected OutputWriter debug;
    protected OutputWriter fileOut;
    protected boolean saveTestResult = true;
    protected boolean gcj = false;

    protected void init() {
      if (local) {
        debug = new OutputWriter(System.err);
        if (saveTestResult) {
          fileOut = OutputWriter.toFile(SAVE_RESULT_FILE);
        }
      } else {
        debug = new OutputWriter(new NullOutputStream());
      }
    }

    public void solve(int testNumber, InputReader in, OutputWriter out) {
      if (firstTest) {
        init();
        precalc();
        firstTest = false;
      }

      this.in = in;
      if (local && saveTestResult) {
        this.out = new SplittingOutputWriter(out, fileOut);
      } else {
        this.out = out;
      }

      preSolve(testNumber);
      solve(testNumber);
      postSolve(testNumber);
    }

    protected void precalc() {

    }

    protected void preSolve(int testNumber) {
      if (gcj) {
        out.printf("Case #%d: ", testNumber);
      }
    }

    public abstract void solve(int testNumber);

    protected void postSolve(int testNumber) {
      out.flush();
      debug.flush();
    }

  }

  static class NullOutputStream extends OutputStream {
    public void write(int b) throws IOException {
      // nothing
    }

  }

  static class OutputWriter extends PrintWriter {
    public static OutputWriter toFile(String fileName) {
      try {
        return new OutputWriter(fileName);
      } catch (FileNotFoundException e) {
        throw new RuntimeException(e);
      }
    }

    public void close() {
      super.close();
    }

    public OutputWriter(String fileName) throws FileNotFoundException {
      super(fileName);
    }

    public OutputWriter(OutputStream outputStream) {
      super(outputStream, true);
    }

    public OutputWriter(Writer writer) {
      super(writer, true);
    }

  }

  static class InputReader {
    private BufferedReader br;
    private StringTokenizer in;

    public InputReader(String fileName) {
      try {
        br = new BufferedReader(new FileReader(fileName));
      } catch (IOException e) {
        throw new RuntimeException(e);
      }
    }

    public InputReader(InputStream inputStream) {
      br = new BufferedReader(new InputStreamReader(inputStream));
    }

    private boolean hasMoreTokens() {
      while (in == null || !in.hasMoreTokens()) {
        String s = nextLine();
        if (s == null) {
          return false;
        }
        in = new StringTokenizer(s);
      }
      return true;
    }

    public String nextString() {
      return hasMoreTokens() ? in.nextToken() : null;
    }

    public String nextLine() {
      try {
        in = null;
        return br.readLine();
      } catch (Exception e) {
        e.printStackTrace();
        return null;
      }
    }

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

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

  }

  static class SplittingOutputWriter extends OutputWriter {
    private final OutputWriter[] outputWriters;

    public SplittingOutputWriter(OutputWriter... outputWriters) {
      super(new OutputStream() {

        public void write(int b) throws IOException {
          for (OutputWriter outputWriter : outputWriters) {
            outputWriter.write(b);
          }
        }
      });

      this.outputWriters = outputWriters;
    }

    public void flush() {
      for (OutputWriter outputWriter : outputWriters) {
        outputWriter.flush();
      }
    }

    public void close() {
      for (OutputWriter outputWriter : outputWriters) {
        outputWriter.close();
      }
    }

  }
}