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.util.*;
import java.lang.*;
import java.io.*;
import java.math.*;

/**
 * Author    : joney_000[developer.jaswant@gmail.com]
 * Algorithm : Extended Euclid Algo: find 3 things X, Y, GCD(A, B) Such that X * A + Y * B = GCD(A, B)
 *             Time : O(MAX(A, B)) Space : O(MAX(A, B))
 * Platform  : Codeforces
 * Ref       : https://www.hackerearth.com/practice/math/number-theory/basic-number-theory-1/tutorial/
 */

public class A{ 
  
  private InputStream inputStream ;
  private OutputStream outputStream ;
  private FastReader in ;
  private PrintWriter out ;
  
  private final int BUFFER = 100005;
  
  private final long mod = 1000000000+7;
  private final int  INF  = Integer.MAX_VALUE;
  private final long INF_L  = Long.MAX_VALUE;

  public A(){}
  public A(boolean stdIO)throws FileNotFoundException{
    // stdIO = false;
    if(stdIO){
      inputStream = System.in;
      outputStream = System.out;
    }else{
      inputStream = new FileInputStream("input.txt");
      outputStream = new FileOutputStream("output.txt");
    }
    in = new FastReader(inputStream);
    out = new PrintWriter(outputStream);
  }
  
  int MAXN = (int)3e5 + 1;
  int a[] = new int[MAXN];
  int pos[] = new int[MAXN];
  int ans = 0;
  int x[] = new int[5 * MAXN];
  int y[] = new int[5 * MAXN];
  int idx = 0;
  void run()throws Exception {
    int n = i();
    for(int i = 1; i <= n; i++){
      a[i] = i();
      pos[a[i]] = i;
    }
    // LinkedList<Pair> ans = new LinkedList<>();
    for(int i = 1; i <= n; i++){
      if(i == pos[i])continue;

      if(2 * Math.abs(pos[i] - i) < n){
        int p1 = Math.min(i, pos[i]);
        int p2 = Math.max(i, pos[i]);
        if (p2 <= n/2){ // both first half
          // ans.add(new Pair(p1, n));
          // ans.add(new Pair(p2, n));
          // ans.add(new Pair(p1, n));
          ans += 3;
          ++idx;
          x[idx] = p1; y[idx] = n;
          ++idx;
          x[idx] = p2; y[idx] = n;
          ++idx;
          x[idx] = p1; y[idx] = n;
          

        }else if(p1 > n/2){ // both second half
          // ans.add(new Pair(p1, 1));
          // ans.add(new Pair(p2, 1));
          // ans.add(new Pair(p1, 1));
          ans += 3;
          ++idx;
          x[idx] = p1; y[idx] = 1;
          ++idx;
          x[idx] = p2; y[idx] = 1;
          ++idx;
          x[idx] = p1; y[idx] = 1;
        }else{
          // ans.add(new Pair(p1, n));
          // ans.add(new Pair(p2, 1));

          // ans.add(new Pair(1, n));

          // ans.add(new Pair(p1, n));
          // ans.add(new Pair(p2, 1));
          ans += 5;
          ++idx;
          x[idx] = p1; y[idx] = n;
          ++idx;
          x[idx] = p2; y[idx] = 1;

          ++idx;
          x[idx] = 1; y[idx] = n;
          
          ++idx;
          x[idx] = p1; y[idx] = n;
          ++idx;
          x[idx] = p2; y[idx] = 1;
          
        }

      }else{
        // ans.add(new Pair(i, pos[i]));
          ans += 1;
          ++idx;
          x[idx] = i; y[idx] = pos[i];
          
      }

      int t = a[i];
      pos[t] = pos[i];
      a[pos[t]] = t;

      a[i] = i;
      pos[i] = i;
    }

    out.write(""+ans+"\n");
    for(int i = 1; i <= ans; i++){
      out.write(""+x[i] +" "+y[i]+"\n");
      // out.flush();
      // if(Math.abs(p.a - p.b) < n/2){
      //   throw new Exception();
      // }
    }
  }
  
  void clear(){

  }

  long gcd(long a, long b){
    if(b == 0)return a;
    return gcd(b, a % b);
  }

  long lcm(long a, long b){
    if(a == 0 || b == 0)return 0;
    return (a * b)/gcd(a, b);
  }

  long mulMod(long a, long b, long mod){
    if(a == 0 || b == 0)return 0;
    if(b == 1)return a;
    long ans = mulMod(a, b/2, mod);
    ans = (ans * 2) % mod;
    if(b % 2 == 1)ans = (a + ans)% mod;
    return ans;
  }

  long pow(long a, long b, long mod){
    if(b == 0)return 1;
    if(b == 1)return a;
    long ans = pow(a, b/2, mod);
    ans = mulMod(ans, ans, mod);
    if(ans >= mod)ans %= mod;

    if(b % 2 == 1)ans = mulMod(a, ans, mod);
    if(ans >= mod)ans %= mod;

    return ans;
  }

  // 20*20   nCr Pascal Table
  long[][] ncrTable(){
    long ncr[][] = new long[21][21];

    for(int i = 0; i <= 20; i++){
      ncr[i][0] = ncr[i][i] = 1L;
    }

    for(int j = 0; j <= 20; j++){
      for(int i = j + 1; i <= 20; i++){
        ncr[i][j] = ncr[i-1][j] + ncr[i-1][j-1];
      }
    }

    return ncr;
  }

  int i()throws Exception{
    return in.nextInt();
  }

  long l()throws Exception{
    return in.nextLong();
  }

  double d()throws Exception{
    return in.nextDouble();
  }

  char c()throws Exception{
    return in.nextCharacter();
  }

  String s()throws Exception{
    return in.nextLine();
  }

  BigInteger bi()throws Exception{
    return in.nextBigInteger();
  }
  
  private void closeResources(){
    out.flush();
    out.close();
    return;
  }

//  IMP: roundoff upto 2 digits 
//  double roundOff = Math.round(a * 100.0) / 100.0;
//                    or
//  System.out.printf("%.2f", val);

//  print upto 2 digits after decimal
//  val = ((long)(val * 100.0))/100.0;    

  public static void main(String[] args) throws java.lang.Exception{
  
    A driver = new A(true);
    driver.run();
    driver.closeResources();
  }
}

class FastReader{

  private boolean finished = false;

  private InputStream stream;
  private byte[] buf = new byte[4 * 1024];
  private int curChar;
  private int numChars;
  private SpaceCharFilter filter;

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

  public int read(){
    if (numChars == -1){
      throw new InputMismatchException ();
    }
    if (curChar >= numChars){
      curChar = 0;
      try{
        numChars = stream.read (buf);
      } catch (IOException e){
        throw new InputMismatchException ();
      }
      if (numChars <= 0){
        return -1;
      }
    }
    return buf[curChar++];
  }

  public int peek(){
    if (numChars == -1){
      return -1;
    }
    if (curChar >= numChars){
      curChar = 0;
      try{
        numChars = stream.read (buf);
      } catch (IOException e){
        return -1;
      }
      if (numChars <= 0){
        return -1;
      }
    }
    return buf[curChar];
  }

  public int nextInt(){
    int c = read ();
    while (isSpaceChar (c))
      c = read ();
    int sgn = 1;
    if (c == '-'){
      sgn = -1;
      c = read ();
    }
    int res = 0;
    do{
      if(c==','){
        c = read();
      }
      if (c < '0' || c > '9'){
        throw new InputMismatchException ();
      }
      res *= 10;
      res += c - '0';
      c = read ();
    } while (!isSpaceChar (c));
    return res * sgn;
  }

  public long nextLong(){
    int c = read ();
    while (isSpaceChar (c))
      c = read ();
    int sgn = 1;
    if (c == '-'){
      sgn = -1;
      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 res * sgn;
  }

  public String nextString(){
    int c = read ();
    while (isSpaceChar (c))
      c = read ();
    StringBuilder res = new StringBuilder ();
    do{
      res.appendCodePoint (c);
      c = read ();
    } while (!isSpaceChar (c));
    return res.toString ();
  }

  public boolean isSpaceChar(int c){
    if (filter != null){
      return filter.isSpaceChar (c);
    }
    return isWhitespace (c);
  }

  public static boolean isWhitespace(int c){
    return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
  }

  private String readLine0(){
    StringBuilder buf = new StringBuilder ();
    int c = read ();
    while (c != '\n' && c != -1){
      if (c != '\r'){
        buf.appendCodePoint (c);
      }
      c = read ();
    }
    return buf.toString ();
  }

  public String nextLine(){
    String s = readLine0 ();
    while (s.trim ().length () == 0)
      s = readLine0 ();
    return s;
  }

  public String nextLine(boolean ignoreEmptyLines){
    if (ignoreEmptyLines){
      return nextLine ();
    }else{
      return readLine0 ();
    }
  }

  public BigInteger nextBigInteger(){
    try{
      return new BigInteger (nextString ());
    } catch (NumberFormatException e){
      throw new InputMismatchException ();
    }
  }

  public char nextCharacter(){
    int c = read ();
    while (isSpaceChar (c))
      c = read ();
    return (char) c;
  }

  public double nextDouble(){
    int c = read ();
    while (isSpaceChar (c))
      c = read ();
    int sgn = 1;
    if (c == '-'){
      sgn = -1;
      c = read ();
    }
    double res = 0;
    while (!isSpaceChar (c) && c != '.'){
      if (c == 'e' || c == 'E'){
        return res * Math.pow (10, nextInt ());
      }
      if (c < '0' || c > '9'){
        throw new InputMismatchException ();
      }
      res *= 10;
      res += c - '0';
      c = read ();
    }
    if (c == '.'){
      c = read ();
      double m = 1;
      while (!isSpaceChar (c)){
        if (c == 'e' || c == 'E'){
          return res * Math.pow (10, nextInt ());
        }
        if (c < '0' || c > '9'){
          throw new InputMismatchException ();
        }
        m /= 10;
        res += (c - '0') * m;
        c = read ();
      }
    }
    return res * sgn;
  }

  public boolean isExhausted(){
    int value;
    while (isSpaceChar (value = peek ()) && value != -1)
      read ();
    return value == -1;
  }

  public String next(){
    return nextString ();
  }

  public SpaceCharFilter getFilter(){
    return filter;
  }

  public void setFilter(SpaceCharFilter filter){
    this.filter = filter;
  }

  public interface SpaceCharFilter{
    public boolean isSpaceChar(int ch);
  }
}

class Pair implements Comparable<Pair>{
  public int a;
  public int b;
   
  public Pair(){
    this.a = 0;
    this.b = 0;
  }

  public Pair(int a, int b){
    this.a = a;
    this.b = b;
  }

  public int compareTo(Pair p){
    if(this.a == p.a){
     return this.b - p.b;  
   }
   return this.a - p.a; 
  }

  @Override
  public String toString(){
    return "a = " + this.a + " b = " + this.b;
  }
}