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.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.lang.reflect.Array;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.BitSet;
import java.util.Collections;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Random;
import java.util.Set;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;

public class q5 {
	
	
	public static void main(String[] args) throws IOException {
		
		Reader.init(System.in);
		PrintWriter out=new PrintWriter(System.out);
		StringBuffer output=new StringBuffer("");
		int n=Reader.nextInt();
		int h=n/2;
		HashMap<Integer,Integer> map=new HashMap<Integer,Integer>(),rmap=new HashMap<Integer,Integer>();
		for(int i=1;i<=n;i++) {
			int a=Reader.nextInt();
			map.put(a, i);
			rmap.put(i, a);
		}
	//	int steps=0;
		ArrayList<NoD> ans=new ArrayList<NoD>();
		for(int i=1;i<=h;i++) {
			int a2=map.get(i+h);
			if(a2>=i+h) {
				if(a2!=i+h) {
					ans.add(new NoD(i,a2));
					ans.add(new NoD(i,i+h));
					int el=rmap.get(i);
					map.put(el, a2);rmap.put(a2, el);
					int el2=rmap.get(i+h);
					map.put(el2, i);rmap.put(i, el2);
				}
			}
			else {
				ans.add(new NoD(a2,a2+h));
				ans.add(new NoD(i,a2+h));
				ans.add(new NoD(i,i+h));
				int el1=rmap.get(a2+h);
				map.put(el1, a2);rmap.put(a2, el1);
				int el2=rmap.get(i);
				map.put(el2, a2+h);
				rmap.put(a2+h, el2);
				el2=rmap.get(i+h);
				map.put(el2, i);
				rmap.put(i, el2);
			}
			int a1=map.get(i);
			if(a1>=i+h) {
				ans.add(new NoD(i,a1));
				int el=rmap.get(i);
				map.put(el, a1);
				rmap.put(a1, el);
			}
			else if(a1!=i) {
				ans.add(new NoD(a1,a1+h));
				ans.add(new NoD(i,a1+h));
				int el=rmap.get(a1+h);
				map.put(el, a1);rmap.put(a1, el);
				el=rmap.get(i);
				map.put(el, a1+h);
				rmap.put(a1+h, el);
				
			}
			map.remove(i);map.remove(i+h);rmap.remove(i);rmap.remove(i+h);
		}
		out.println(ans.size());
		for(NoD a:ans) out.println(a.s);
		
		out.flush();
	}
}



class NoD{
	int a;int b;
	String s;

	NoD(int aa,int bb){
		a=aa;b=bb;
		s=a+" "+b;
		
	}
	
//	NoD(int aa,int bb,int cc){
//		a=aa;b=bb;c=cc;
//	}
//	NoD(long m,long l,long r,long t){
//		ms=m;ls=l;rs=r;ts=t;
//	}
	@Override
	public boolean equals(Object o) {
		if(o!=null && o.getClass()==getClass()) {
			NoD c= (NoD) o;
			return c.a==a && c.b==b;
		}
		return false;
	}
	@Override
	public int hashCode() {
		return s.hashCode();
	}
}
class DisJoint {
	int[] arr;
	int[] parent;
	int[] rank;
	DisJoint(int n){
		arr=new int[n+1];
		parent=new int[n+1];
		rank=new int[n+1];
		for(int i=1;i<=n;i++) {
			arr[i]=i;
			parent[i]=i;
			rank[i]=0;
		}
	}

	int find(int value) {
		int par=parent[value];
		if(par==value)
			return par;
		parent[value]=find(par);
		return parent[value];
	}
	
	void union(int data1,int data2) {
		int parent1=find(data1);
		int parent2=find(data2);
		if(parent1!=parent2) {
			if(rank[parent1]>=rank[parent2]) {
				parent[parent2]=parent1;
				if(rank[parent1]==rank[parent2])
					rank[parent1]++;
			}
			else {
				parent[parent1]=parent2;
			}
		}
		
	}
	

}

class Seg{
	long[] st;
	long[] arr;
	long[] lazy;
	Seg(int n){
		st=new long[4*n];
		//lazy=new long[4*n];
		
	}
	void build(int index,int low,int high) {
		if(low==high) {
			st[index]=arr[low];
		}
		else {
			int middle=(low+high)/2;
			build(2*index+1,low,middle);
			build(2*index+2,middle+1,high);
			st[index]=Math.min(st[2*index+1], st[2*index+2]);
		}
	}
	
	long query(int index,int low,int high, int ql,int qh) {
//		if(lazy[index]!=0) {
//			st[index]+=lazy[index];
//			if(low<high) {
//				lazy[2*index+1]+=lazy[index];
//				lazy[2*index+2]+=lazy[index];
//				
//			}
//			lazy[index]=0;
//		}
		
		if(ql<=low && high<=qh) {
			return st[index];
		}
		else if(!(ql>high || qh<low)) {
			int middle=(low+high)/2;
			long left=query(2*index+1,low,middle,ql,qh);
			long right=query(2*index+2,middle+1,high,ql,qh);
			//st[index]=Math.max(st[2*index+1], st[2*index+2]);
			return Math.max(left,right);
			
		}
		return 0;
	}
	
	
	void u1(int index, int low,int high, int pos,long v) {
//		if(lazy[index]!=0) {
//			st[index]+=lazy[index];
//			if(low<high) {
//				lazy[2*index+1]+=lazy[index];
//				lazy[2*index+2]+=lazy[index];
//				
//			}
//			lazy[index]=0;
//		}
		if(low==high) {
			st[index]=v;
		}
		else {
			int middle=(low+high)/2;
			if(pos<=middle) u1(2*index+1,low,middle,pos,v);
			else u1(2*index+2,middle+1,high,pos,v);
			st[index]=Math.max(st[2*index+1],st[2*index+2]);
		}
	}
	
	
}
class Reader {
    static BufferedReader reader;
    static StringTokenizer tokenizer;
    /** call this method to initialize reader for InputStream */
    static void init(InputStream input) {
        reader = new BufferedReader(
                     new InputStreamReader(input) );
        tokenizer = new StringTokenizer("");
    }
    /** get next word */
    static String nextLine() throws IOException{
    	return reader.readLine();
    }
    static String next() throws IOException {
        while ( ! tokenizer.hasMoreTokens() ) {
            //TODO add check for eof if necessary
            tokenizer = new StringTokenizer(
                   reader.readLine() );
        }
        return tokenizer.nextToken();
    }
    static int nextInt() throws IOException {
        return Integer.parseInt( next() );
    }
    static long nextLong() throws IOException {
        return Long.parseLong( next() );
    }
    static double nextDouble() throws IOException {
        return Double.parseDouble( next() );
    }
}