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


 public class Main {
	public static InputReader in;
    public static PrintWriter pw;



	public static void main(String args[]) {
		new Thread(null, new Runnable() {
            public void run() {
                try{
                    solve();
                }
                catch(Exception e){
                    e.printStackTrace();
                }
            }
        }, "1", 1 << 26).start();
    }
	static TreeSet<Integer> set;
	static ArrayList<Pair> g[];
	static boolean visited[];
	static long edje=0;
    static boolean vis[];
	static int parent[];
	static int col[];
	static boolean[] vis1;
	static int Ans=0;
	static int min=Integer.MAX_VALUE;
	static int val[];
	static int degree[];
	static int a[];
	static int f[];
	static  long total=0;
	static HashSet<String> s;
	static int distance[];
	public static void solve(){
	
		 in = new InputReader(System.in);
		 pw = new PrintWriter(System.out);
	     int n=in.nextInt();
	     int prime[]=new int[100007];
	     prime[0]=1;
	     prime[1]=1;
	     for(int i=2;i*i<100007;i++)
	    	 if(prime[i]==0)
	    		 for(int j=i*i;j<100007;j+=i)
	    			 prime[j]=1;
	     int small[]=new int[100005];
	     int temp1=2;
	     for(int i=2;i<100005;i++)
	     {
	    	// small[i]=temp;
	    	 if(prime[i]==0)
	    		 temp1=i;
	    	 small[i]=temp1;
	     }
	     int a[]=new int[n+1];
	     for(int i=1;i<=n;i++)
	    	 a[i]=in.nextInt();
	     int index[]=new int[n+1];
	     for(int i=1;i<=n;i++)
	     {
	    	 index[a[i]]=i;
	     }
	     int b[]=Arrays.copyOf(a, n);
	     Arrays.sort(b);
	     ArrayList<String> ans=new ArrayList<String>();
	     for(int i=1;i<=n;i++)
	     {
	    	 if(index[i]==i)
	    		 continue;
	    	 
	    		 int diff=index[i]-i;
	    		 diff++;
	    		 int current=index[i];
	    		 boolean bool=true;
	    		 int Original=i;
	    		 while(diff>0)
	    		{
	    		    diff=current-i;
	    		    diff++;
	    		 //   System.out.print(diff+" ");
	    			int SmallPrime=small[diff];
	    			int Decrease=current-SmallPrime+1;
	    			int temp=a[current];
	    			a[current]=a[Decrease];
	    			a[Decrease]=temp;
	    			temp=index[a[current]];
	    			index[a[current]]=index[a[Decrease]];
	    			index[a[Decrease]]=temp;
	    			ans.add(Decrease+" "+current);
	    			current=Decrease;
	    			if(current==Original)
	    			{
	    				break;
	    			}
	    			else if(current==(Original+1))
	    			{
	    				temp=a[current];
	    				a[current]=a[current-1];
	    				a[current-1]=temp;
	    				temp=index[a[current]];
	    				index[a[current]]=index[a[current-1]];
		    			index[a[current-1]]=temp;
		    			ans.add((current-1)+ " "+(current));
		    			break;
	    			}
	    		 }
	    		 
	    //	for(int j=1;j<=n;j++)
	    	//System.out.print(index[j]+" ");
	    //	System.out.println();
	     }
	     System.out.println(ans.size());
	     for(String x:ans)
	    	 System.out.println(x+ " ");
	   //for(int i=1;i<=n;i++)
	 //    System.out.println(a[i]);
	    		 
	      
	}

	/*public static void dfs(int curr)
	{
		vis[curr]=true;
		int trees=0;
		for(int x:g[curr])
		{
			if(!vis[x]&&x!=1)
			{
			trees++;
			if(!s.contains(curr+" "+x))
				total+=cost[curr][x];
			dfs(x);
			}
	    }
		if(trees==0)
		{
			if(!s.contains(curr+" "+1))
				total+=cost[1][curr];
		}
	}
	public static void dfs1(int curr,int parent)
	{
	val[curr]=a[curr];
	for(int x:g[curr])
	{
	       if(x!=parent)
	       {
	    	   dfs1(x,curr);
	    	   val[curr]+=val[x];
	      }
	
	}
	}
	public static void dfs2(int curr,int parent)
	{
		f[curr]=val[curr];
		for(int x:g[curr])
		{
			if(x!=parent)
			{
				dfs2(x,curr);
				f[curr]+=f[x];
			}
		}
	}
	
	
	 
/*    public static void dfs2(int curr)
    {
    if(st[col[curr]].isEmpty())
    {
    ans[curr]=-1;	
    }
    else
    {
    	ans[curr]=st[col[curr]].peek();
    }
    st[col[curr]].push(curr);
    for(int x:g[curr])
    {
    	dfs2(x);
    }
    st[col[curr]].pop();
    	
    }
    
  
	public static void dfs1(int curr)
	{
		visited[curr]=true;
		for(int next:g[curr])
		{
			edje++;
			if(!visited[next])
				dfs1(next);
		}
	}
	
	public static void dfs(int curr,int prev)
		{
		val[curr]=1;
			for(int x:g[curr])
			{
				if(x!=prev)
				{
		            dfs(x,curr);
		            val[curr]+=val[x];
					
			    }
			}
		}*/
	
		public static long power(long a,long b)
		{
			long result=1;
			while(b>0)
			{
				if(b%2==1)
					result*=a;
				a=a*a;
				b/=2;
			}
			return result;
		}
				public static long pow(long n,long p,long m)
	{
		 long  result = 1;
		  if(p==0)
		    return 1;
		if (p==1)
		    return n;
		while(p!=0)
		{
		    if(p%2==1)
		        result *= n;
		    if(result>=m)
		    result%=m;
		    p >>=1;
		    n*=n;
		    if(n>=m)
		    n%=m;
		}
		return result;
	}
	static class Pair implements Comparable<Pair>{
	int fir;
		int sec;
		Pair(int mr,int i){
	     	fir=mr;
			sec=i;
			
		}
		@Override
		public int compareTo(Pair o) {
		//	if(o.val<this.val)
		
			return 1;
			
			//else 
				//return -1;
			
			}
		
	}
	public static long gcd(long a, long b) {
		  if (b == 0) return a;
		  return gcd(b, a%b);
		}
	static class InputReader {
 
		private InputStream stream;
		private 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 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 boolean isSpaceChar(int c) {
			if (filter != null)
				return filter.isSpaceChar(c);
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}
 
		public interface SpaceCharFilter {
			public boolean isSpaceChar(int ch);
		}
	}
}
