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.math.BigInteger; 
import java.util.*;



//Mann Shah [ DAIICT ].
//fast io

public class Main {
	static int mod = (int) (1e9+7);
	static InputReader in;
    static PrintWriter out;
   
    
    public static ArrayList <Pair> ans = new ArrayList <Pair> ();
	public static int[] a;
	public static  int[] pos;
	
	public static void swap(int u, int v) {
		ans.add( new Pair(u, v));
		int temp = a[u];
		a[u]=a[v];
		a[v]=temp;
		pos[a[u]]=u;
		pos[a[v]]=v;
	}
 
		public static void main(String args[] )  {
			
			in = new InputReader(System.in);
	       out = new PrintWriter(System.out);
	       int n = in.nextInt();
			 a = new int[n+1];
			 pos = new int[n+1];
			for(int i=1;i<=n;i++) {
				a[i]=in.nextInt();
				pos[a[i]] = i;
			}
			for(int i=1;i<=n;i++) {
				if(a[i]==i) {
					continue;
				}
				if(i<=n/2) {
					if(pos[i] <= n/2)
					{
						swap(pos[i],n);
						swap(i,n);
					}
					else if(i==1)
					{
						swap(pos[i],1);
					}
					else if(pos[i]==n) {
						swap(pos[i],i);
					}
					else {
						swap(1,pos[i]);
						swap(1,n);
						swap(i,n);
						swap(1,pos[1]);
					}
				}
				else {
					swap(1,pos[i]);
					swap(1,i);
					swap(1,pos[1]);
				}
			}
			out.println(ans.size());
			for(int i=0;i<ans.size();i++){
			    out.println(ans.get(i).x+" "+ans.get(i).y);
			}
	       out.close();
		}
		

		
		static class InputReader
	    {

	        private final InputStream stream;
	        private final byte[] buf = new byte[8192];
	        private int curChar, snumChars;
	        private SpaceCharFilter filter;

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

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

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

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

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

	        public long[] nextLongArray(int n)
	        {
	                long a[] = new long[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextLong();
	                }
	                return a;
	        }

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

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

	        public boolean isSpaceChar(int c)
	        {
	                if (filter != null)
	                        return filter.isSpaceChar(c);
	                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	        }

	        private boolean isEndOfLine(int c)
	        {
	                return c == '\n' || c == '\r' || c == -1;
	        }

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

	    }
		
}



//Pair arr[] = new Pair[n]; 
//arr[0] = new Pair(10, 20); 
 class Pair { 
    int x; 
    int y; 
  
    // Constructor 
public Pair(int x, int y) 
    { 
        this.x = x; 
        this.y = y; 
    } 
} 
 class Compare { 
	  //void return by default.
    static Pair[] compare(Pair arr[], int n) 
    { 
        // Comparator to sort the pair according to first element.
        Arrays.sort(arr, new Comparator<Pair>() { 
            @Override public int compare(Pair p1, Pair p2) 
            { 
                return p1.x - p2.x; 
            } 
        }); 
        
        
        return arr;
       /* for (int i = 0; i < n; i++) { 
            System.out.print(arr[i].x + " " + arr[i].y + " "); 
        } 
        System.out.println(); */
    } 
} 




class couple implements Comparable<couple>
{ int x,y;
  public couple(int m,int f) {
 	 x=m;
 	 y=f;
  }
	public int compareTo(couple o) {
		
		 
		return x-o.x;
	}  
}