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.BigDecimal;
import java.math.BigInteger;
import java.math.RoundingMode;
import java.text.DecimalFormat;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main
{
   static long mod=(long)(1e+9 + 7);
   //static long mod=(long)998244353;
   
   static int[] sieve;
   static ArrayList<Integer> primes;
   static PrintWriter out;
   static fast s;
   static StringBuilder fans;
  
   public static void swap(int i,int j,int[] a,HashMap<Integer,Integer> hm)
   {
   	hm.put(a[i],j);
   	hm.put(a[j],i);
   	
   	int temp=a[i];
   	a[i]=a[j];
   	a[j]=temp;
   }
   
   public static void solve()
   {
   	int n=s.nextInt();
   	int bound=(n+1)/2;
   	
   	ArrayList<Integer> arr=new ArrayList<Integer>();
   	int a[]=new int[n];
   	for(int i=0;i<n;i++) {a[i]=s.nextInt();arr.add(a[i]);}
   	
   	Collections.sort(arr);
   	int b[]=new int[n];
   	for(int i=0;i<n;i++) b[i]=arr.get(i);
   	
   	HashMap<Integer,Integer> hm=new HashMap<Integer,Integer>();
   	for(int i=0;i<n;i++) hm.put(a[i], i);
   	
   	int swaps=0;
   	
   	for(int i=0;i<arr.size();i++)
   		{
   			//for(int k=0;k<a.length;k++) System.out.print(a[k]+" ");
   			//System.out.println();
   			
   			int cur_element=a[i];
   			int req_element=arr.get(i);
   			
   			if(cur_element==req_element) continue;
   			
   			int cur_index=i;
   			int req_index=hm.get(req_element);
   			
   			if(req_index-cur_index>=bound)
   				{
   					swap(cur_index,req_index,a,hm);
   					swaps++;
   					fans.append((cur_index+1)+" "+(req_index+1)+"\n");
   				}
   			else
   				{
   					if(req_index+bound<n)
   						{
   							swap(req_index,req_index+bound,a,hm);
   							swap(cur_index,req_index+bound,a,hm);
   							
   							fans.append((req_index+1)+" "+(req_index+bound+1)+"\n");
   							fans.append((cur_index+1)+" "+(req_index+bound+1)+"\n");
   							swaps+=2;
   						}
   					else if(cur_index-bound>=0)
   						{
   							swap(req_index,cur_index-bound,a,hm);
   							swap(cur_index-bound,cur_index,a,hm);
   							swap(req_index,cur_index-bound,a,hm);
   							
   							fans.append((req_index+1)+" "+(cur_index-bound+1)+"\n");
   							fans.append((cur_index-bound+1)+" "+(cur_index+1)+"\n");
   							fans.append((req_index+1)+" "+(cur_index-bound+1)+"\n");
   							swaps+=3;
   						}
   					else
   						{
   							swap(req_index,0,a,hm);
   							swap(0,n-1,a,hm);
   							swap(cur_index,n-1,a,hm);
   							swap(0,n-1,a,hm);
   							swap(0,req_index,a,hm);
   							
   							fans.append((req_index+1)+" "+(1)+"\n");
   							fans.append((1)+" "+(n)+"\n");
   							fans.append((cur_index+1)+" "+(n)+"\n");
   							fans.append((1)+" "+(n)+"\n");
   							fans.append((1)+" "+(req_index+1)+"\n");
   							
   							swaps+=5;
   						}
   				}
   		}
   	
   	System.out.println(swaps);
   	System.out.println(fans);
   }
   
   public static void main(String[] args) throws java.lang.Exception
   {	  	
	     s = new fast();
	     out=new PrintWriter(System.out);
	     fans=new StringBuilder("");
		    
	     int t=1;
	    
	     while(t>0)
	    	 {
	    		 solve();
	    		 t--;
	    	 }
   }
  
 
 
static class fast {   
	
	    private InputStream i;
		private byte[]  buf = new byte[1024];
		private int curChar;
		
		private int numChars;
		
		//Return floor log2n
		public static long log2(long bits) // returns 0 for bits=0
			{
			    int log = 0;
			    if( ( bits & 0xffff0000 ) != 0 ) { bits >>>= 16; log = 16; }
			    if( bits >= 256 ) { bits >>>= 8; log += 8; }
			    if( bits >= 16  ) { bits >>>= 4; log += 4; }
			    if( bits >= 4   ) { bits >>>= 2; log += 2; }
			    return log + ( bits >>> 1 );
			}
		
		public static boolean next_permutation(int a[])
		   {
			   int i=0,j=0;int index=-1;	   
			   int n=a.length;
			   
			   for(i=0;i<n-1;i++)
				   if(a[i]<a[i+1]) index=i;
			   
			   if(index==-1) return false;
			   i=index;
 
			  
			   for(j=i+1;j<n && a[i]<a[j];j++);
 
			   int temp=a[i];
			   a[i]=a[j-1];
			   a[j-1]=temp;
			   	   
			   for(int p=i+1,q=n-1;p<q;p++,q--)
			   {
				   temp=a[p];
				   a[p]=a[q];
				   a[q]=temp;
			   }
			   
			   return true;
		   }
		   
		   
		public static void division(char ch[],int divisor)
		   {
			   int div=Character.getNumericValue(ch[0]); int mul=10;int remainder=0;
			   StringBuilder quotient=new StringBuilder("");
			   for(int i=1;i<ch.length;i++)
			   {
				   div=div*mul+Character.getNumericValue(ch[i]);	
				   if(div<divisor) {quotient.append("0");continue;}
				   quotient.append(div/divisor);
				   div=div%divisor;mul=10;
				   
			   } 
			   remainder=div;
			   while(quotient.charAt(0)=='0')quotient.deleteCharAt(0);	   
			   System.out.println(quotient+" "+remainder);	  
		   }
		
		public static void sieve(int size)
		{
			sieve=new int[size+1];
			
			primes=new ArrayList<Integer>();
			
			sieve[1]=1;
			
			for(int i=2;i*i<=size;i++)
			{
				if(sieve[i]==0)
				 {
					for(int j=i*i;j<size;j+=i) {sieve[j]=1;}
				 }
			}
			
			for(int i=2;i<=size;i++)
			{
				if(sieve[i]==0) primes.add(i);
			}
		}
		
		public static long pow(long n, long b, long MOD)
		   {
		       long x=1;long y=n; 
		       while(b > 0)
		       {
		           if(b%2 == 1)
		           {
		               x=x*y;
		               if(x>MOD) x=x%(MOD);
		           }
		           y = y*y;
		           if(y>MOD) y=y%(MOD); 
		           b >>= 1;
		       }
		       return x;
		   }
 
 
		public static long mod_inv(long n,long mod)
		{
			return pow(n,mod-2,mod);
		}
		
		//Returns index of highest number less than or equal to key
		 public static int upper(long[] a,int length,long key)
		 {
			    int low = 0;
		        int high = length-1;
		        int ans=-1;
		        
		        while (low <= high) {
		            int mid = (low + high) / 2;
		            if (key >= a[mid]) {
		                ans=mid;
		            	low = mid+1;
		            } else if(a[mid]>key){
		                high = mid - 1;
		            }
		        }
		        return ans;
		}
		
		//Returns index of least number greater than or equal to key
		 public static int lower(long[] a,int length,long key)
		 {
			    int low = 0;
		        int high = length-1;
		        int ans=-1;
		        
		        while (low <= high) {
		            int mid = (low + high) / 2;
		            if (key<=a[mid]) {
		                ans=mid;
		            	high = mid-1;
		            }
		            else{
		            		low=mid+1;
		            	}
		        }
		        return ans;
		} 
		   
		public long gcd(long r,long ans)
		{
			if(r==0) return ans;
			return gcd(ans%r,r);
		}
		public fast() {
			this(System.in);
		}
		public fast(InputStream is) {
			i = is;
		}
		public int read() {
			if (numChars == -1)
				throw new InputMismatchException();
			if (curChar >= numChars) {
				curChar = 0;
				try {
					numChars = i.read(buf);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (numChars <= 0)
					return -1;
			}
			return buf[curChar++];
		}
		public String nextLine() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isEndOfLine(c));
			return res.toString();
		}
		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 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 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 < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			} while (!isSpaceChar(c));
			return res * sgn;
		}
		public boolean isSpaceChar(int c) {
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}
		public boolean isEndOfLine(int c) {
			return c == '\n' || c == '\r' || c == -1;
		}
 
	}	
}