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.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.NoSuchElementException;

public class Main {

	static PrintWriter out;
	static InputReader ir;

	static void solve() {
		int n = ir.nextInt();
		int[] a = ir.nextIntArray(n);
		for (int i = 0; i < n; i++)
			a[i]--;
		int[] p = new int[n];
		for (int i = 0; i < n; i++)
			p[a[i]] = i;
		ArrayList<int[]> l = new ArrayList<>();
		for (int i = 1; i < n - 1; i++) {
			if (a[i] == i)
				continue;
			if (p[i] / (n / 2) == p[a[i]] / (n / 2)) {
				if (p[i] / (n / 2) == 0) {
					l.add(new int[] { p[a[i]] + 1, n });
					l.add(new int[] { p[i] + 1, n });
					l.add(new int[] { p[a[i]] + 1, n });
					int t = a[i];
					a[i] = a[p[i]];
					a[p[i]] = t;
				} else {
					l.add(new int[] { 1, p[a[i]] + 1 });
					l.add(new int[] { 1, p[i] + 1 });
					l.add(new int[] { 1, p[a[i]] + 1 });
					int t = a[i];
					a[i] = a[p[i]];
					a[p[i]] = t;
				}
			} else {
				if (p[i] / (n / 2) == 0) {
					if (Math.abs(p[i] - p[a[i]]) >= n / 2) {
						l.add(new int[] { p[i] + 1, p[a[i]] + 1 });
					} else {
						l.add(new int[] { 1, p[a[i]] + 1 });
						l.add(new int[] { p[i] + 1, n });
						l.add(new int[] { 1, n });
						l.add(new int[] { 1, p[a[i]] + 1 });
						l.add(new int[] { p[i] + 1, n });
					}
					int t = a[i];
					a[i] = a[p[i]];
					a[p[i]] = t;

				} else {
					if (Math.abs(p[i] - p[a[i]]) >= n / 2) {
						l.add(new int[] { p[a[i]] + 1, p[i] + 1 });
					} else {
						l.add(new int[] { 1, p[i] + 1 });
						l.add(new int[] { p[a[i]] + 1, n });
						l.add(new int[] { 1, n });
						l.add(new int[] { 1, p[i] + 1 });
						l.add(new int[] { p[a[i]] + 1, n });

					}
					int t = a[i];
					a[i] = a[p[i]];
					a[p[i]] = t;
				}
			}
			p[a[p[i]]] = p[i];
			p[i] = i;
			// tr(a);
			// tr(p);
		}
		if (a[0] != 0)
			l.add(new int[] { 1, n });
		out.println(l.size());
		for (int i = 0; i < l.size(); i++) {
			out.println(l.get(i)[0] + " " + l.get(i)[1]);
		}
	}

	public static void main(String[] args) {
		ir = new InputReader(System.in);
		out = new PrintWriter(System.out);
		solve();
		out.flush();
	}

	static class InputReader {

		private InputStream in;
		private byte[] buffer = new byte[1024];
		private int curbuf;
		private int lenbuf;

		public InputReader(InputStream in) {
			this.in = in;
			this.curbuf = this.lenbuf = 0;
		}

		public boolean hasNextByte() {
			if (curbuf >= lenbuf) {
				curbuf = 0;
				try {
					lenbuf = in.read(buffer);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (lenbuf <= 0)
					return false;
			}
			return true;
		}

		private int readByte() {
			if (hasNextByte())
				return buffer[curbuf++];
			else
				return -1;
		}

		private boolean isSpaceChar(int c) {
			return !(c >= 33 && c <= 126);
		}

		private void skip() {
			while (hasNextByte() && isSpaceChar(buffer[curbuf]))
				curbuf++;
		}

		public boolean hasNext() {
			skip();
			return hasNextByte();
		}

		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (!isSpaceChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}

		public int nextInt() {
			if (!hasNext())
				throw new NoSuchElementException();
			int c = readByte();
			while (isSpaceChar(c))
				c = readByte();
			boolean minus = false;
			if (c == '-') {
				minus = true;
				c = readByte();
			}
			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res = res * 10 + c - '0';
				c = readByte();
			} while (!isSpaceChar(c));
			return (minus) ? -res : res;
		}

		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			int c = readByte();
			while (isSpaceChar(c))
				c = readByte();
			boolean minus = false;
			if (c == '-') {
				minus = true;
				c = readByte();
			}
			long res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res = res * 10 + c - '0';
				c = readByte();
			} while (!isSpaceChar(c));
			return (minus) ? -res : res;
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}

		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 char[][] nextCharMap(int n, int m) {
			char[][] map = new char[n][m];
			for (int i = 0; i < n; i++)
				map[i] = next().toCharArray();
			return map;
		}
	}

	static void tr(Object... o) {
		out.println(Arrays.deepToString(o));
	}
}