You have an array a[1], a[2], ..., a[n], containing distinct integers from 1 to n. Your task is to sort this array in increasing order with the following operation (you may need to apply it multiple times):

  * choose two indexes, i and j (1 ≤ i < j ≤ n; (j - i + 1) is a prime number); 
  * swap the elements on positions i and j; in other words, you are allowed to apply the following sequence of assignments: tmp = a[i], a[i] = a[j], a[j] = tmp (tmp is a temporary variable). 



You do not need to minimize the number of used operations. However, you need to make sure that there are at most 5n operations.

Input

The first line contains integer n (1 ≤ n ≤ 105). The next line contains n distinct integers a[1], a[2], ..., a[n] (1 ≤ a[i] ≤ n).

Output

In the first line, print integer k (0 ≤ k ≤ 5n) — the number of used operations. Next, print the operations. Each operation must be printed as "i j" (1 ≤ i < j ≤ n; (j - i + 1) is a prime).

If there are multiple answers, you can print any of them.

Examples

Input

3
3 2 1


Output

1
1 3


Input

2
1 2


Output

0


Input

4
4 2 3 1


Output

3
2 4
1 2
2 4
import java.io.*;
import java.util.*;
import java.math.*;

/**
 * Moonsorrow - Jaasta Syntynyt / Varjojen Virta.
 * 
 * @author Gorokhov Nikita (wackloner@gmail.com)
 */

public class C implements Runnable {
	
	class Pair {
		int l, r;
		
		Pair(int l, int r) {
			this.l = l;
			this.r = r;
		}
	}
	
	void solve() {
		int n = nextInt();
		int[] a = new int[n], b = new int[n], pos = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = b[i] = nextInt() - 1;
			pos[a[i]] = i;
		}
		mergeSort(a, 0, n);
		boolean[] prime = new boolean[n + 1];
		Arrays.fill(prime, true);
		for (int i = 2; i * i <= n; i++)
			if (prime[i])
				for (int j = i + i; j <= n; j += i)
					prime[j] = false;
		ArrayList<Pair> ans = new ArrayList<Pair>();
		for (int i = 0; i < n; i++) {
			while (pos[a[i]] != i) {
				for (int j = pos[a[i]] - i + 1; j >= 0; j--)
					if (prime[j]) {
						int ind = pos[a[i]] - j + 1;
						ans.add(new Pair(ind, pos[a[i]]));
						swap(b, ind, pos[a[i]]);
						swap(pos, b[pos[a[i]]], a[i]);
						break;
					}
			}
		}
		println(ans.size());
		for (Pair p : ans)
			println(p.l + 1, p.r + 1);
	}
	
	void swap(int[] a, int i, int j) {
		int tmp = a[i];
		a[i] = a[j];
		a[j] = tmp;
	}
	
	void mergeSort(int[] a, int l, int r) {
		if (r - l > 1) {
			int m = (l + r) / 2;
			mergeSort(a, l, m);
			mergeSort(a, m, r);
			merge(a, l, m, r);
		}
	}
	
	int[] tmp = new int[1_000_000];
	
	void merge(int[] a, int l, int m, int r) {
		int i = l, j = m, cnt = 0;
		while (i < m || j < r)
			if (i == m || j < r && a[i] > a[j])
				tmp[cnt++] = a[j++];
			else
				tmp[cnt++] = a[i++];
		for (int k = 0; k < cnt; k++)
			a[k + l] = tmp[k];
	}
	
	public static void main(String[] args) throws IOException {
		new C().run();
	}
	
	C() {
		this.stream = System.in;
		this.writer = new PrintWriter(System.out);
	}
	
	C(String input, String output) throws IOException {
		File inputFile = new File(input);
		inputFile.createNewFile();
		stream = new FileInputStream(inputFile);
		File outputFile = new File(output);
		outputFile.createNewFile();
		writer = new PrintWriter(outputFile);
	}
	
	public void run() {
		solve();
		writer.close();
	}
	
	void halt() {
		writer.close();
		System.exit(0);
	}
	
	PrintWriter writer;;
	
	void print(Object... objects) {
		for (int i = 0; i < objects.length; i++) {
			if (i != 0)
				writer.print(' ');
			writer.print(objects[i]);
		}
	}
	
	void println(Object... objects) {
		print(objects);
		writer.println();
	}
	
	void printArray(int[] array) {
		for (int i = 0; i < array.length; i++) {
			if (i != 0) writer.print(' ');
			writer.print(array[i]);
		}
		writer.println();
	}
	
	void printArray(long[] array) {
		for (int i = 0; i < array.length; i++) {
			if (i != 0) writer.print(' ');
			writer.print(array[i]);
		}
		writer.println();
	}
	
	void printMatrix(int[][] matrix) {
		for (int i = 0; i < matrix.length; i++)
			printArray(matrix[i]);
	}
	
	void printMatrix(long[][] matrix) {
		for (int i = 0; i < matrix.length; i++)
			printArray(matrix[i]);
	}
	
	/**
	 * Pure Egor's code is straight ahead.
	 */
	
	InputStream stream;
	byte[] buf = new byte[1024];
	int curChar, numChars;
	
	int nextInt() {
		int c = next();
		while (isWhitespace(c))
			c = next();
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = next();
		}
		int res = 0;
		do {
			if (c < '0' || c > '9')
				throw new InputMismatchException();
			res *= 10;
			res += c - '0';
			c = next();
		} while (!isWhitespace(c));
		return res * sgn;
	}
	
	long nextLong() {
		int c = next();
		while (isWhitespace(c))
			c = next();
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = next();
		}
		long res = 0;
		do {
			if (c < '0' || c > '9')
				throw new InputMismatchException();
			res *= 10;
			res += c - '0';
			c = next();
		} while (!isWhitespace(c));
		return res * sgn;
	}
	
	double nextDouble() {
		int c = next();
		while (isWhitespace(c))
			c = next();
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = next();
		}
		double res = 0;
		while (!isWhitespace(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 = next();
		}
		if (c == '.') {
			c = next();
			double m = 1;
			while (!isWhitespace(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 = next();
			}
		}
		return res * sgn;
	}
	
	BigInteger nextBigInteger() {
		try {
			return new BigInteger(nextString());
		} catch (NumberFormatException e) {
			throw new InputMismatchException();
		}
	}
	
	int next() {
		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++];
	}
	
	String nextString() {
		int c = next();
		while (isWhitespace(c))
			c = next();
		StringBuilder res = new StringBuilder();
		do {
			if (Character.isValidCodePoint(c))
				res.appendCodePoint(c);
			c = next();
		} while (!isWhitespace(c));
		return res.toString();
	}
	
	String nextLine() {
		StringBuilder buf = new StringBuilder();
		int c = next();
		while (c != '\n' && c != -1) {
			if (c != '\r')
				buf.appendCodePoint(c);
			c = next();
		}
		return buf.toString();
	}
	
	boolean EOF() {
		int value;
		while (isWhitespace(value = peek()) && value != -1)
			next();
		return value == -1;
	}
	
	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];
	}
	
	boolean isWhitespace(int c) {
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}
}