Problem: Fox Ciel is participating in a party in Prime Kingdom. There are n foxes there (include Fox Ciel). The i-th fox is ai years old.

They will have dinner around some round tables. You want to distribute foxes such that:

  1. Each fox is sitting at some table. 
  2. Each table has at least 3 foxes sitting around it. 
  3. The sum of ages of any two adjacent foxes around each table should be a prime number. 



If k foxes f1, f2, ..., fk are sitting around table in clockwise order, then for 1 ≤ i ≤ k - 1: fi and fi + 1 are adjacent, and f1 and fk are also adjacent.

If it is possible to distribute the foxes in the desired manner, find out a way to do that.

Input

The first line contains single integer n (3 ≤ n ≤ 200): the number of foxes in this party. 

The second line contains n integers ai (2 ≤ ai ≤ 104).

Output

If it is impossible to do this, output "Impossible".

Otherwise, in the first line output an integer m (<image>): the number of tables.

Then output m lines, each line should start with an integer k -=– the number of foxes around that table, and then k numbers — indices of fox sitting around that table in clockwise order.

If there are several possible arrangements, output any of them.

Examples

Input

4
3 4 8 9


Output

1
4 1 2 4 3


Input

5
2 2 2 2 2


Output

Impossible


Input

12
2 3 4 5 6 7 8 9 10 11 12 13


Output

1
12 1 2 3 6 5 12 9 8 7 10 11 4


Input

24
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25


Output

3
6 1 2 3 6 5 4
10 7 8 9 12 15 14 13 16 11 10
8 17 18 23 22 19 20 21 24

Note

In example 1, they can sit around one table, their ages are: 3-8-9-4, adjacent sums are: 11, 17, 13 and 7, all those integers are primes.

In example 2, it is not possible: the sum of 2+2 = 4 is not a prime number.

Solution (in JAVA):

Solution:
//package round290;
import java.io.ByteArrayInputStream;
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.List;

public class C {
	InputStream is;
	PrintWriter out;
	String INPUT = "";
	
	void solve()
	{
		int n = ni();
		int[] a = na(n);
		int oe = 0;
		for(int i = 0;i < n;i++){
			if(a[i] % 2 == 1){
				oe++;
			}else{
				oe--;
			}
		}
		if(oe != 0){
			out.println("Impossible");
			return;
		}
		int[][] as = new int[n][];
		for(int i = 0;i < n;i++){
			as[i] = new int[]{a[i], i};
		}
		
		long[] isp = isp(30000);
		
		List<Edge> es = new ArrayList<Edge>();
		int src = n, sink = n+1;
		for(int i = 0;i < n;i++){
			if(a[i] % 2 == 0){
				es.add(new Edge(src, i, 2));
				for(int j = 0;j < n;j++){
					if(isp[a[i]+a[j]>>>6]<<~(a[i]+a[j])<0){
						es.add(new Edge(i, j, 1));
					}
				}
			}else{
				es.add(new Edge(i, sink, 2));
			}
		}
		
		Edge[][] g = compileWD(n+2, es);
		long F = maximumFlowDinic(g, src, sink);
		if(F != (n/2)*2){
			out.println("Impossible");
			return;
		}
		
		int[] from = new int[n];
		int[] to = new int[n];
		int q = 0;
		for(int i = 0;i < n;i++){
			if(a[i] % 2 == 0){
				for(Edge e : g[i]){
					if(e.flow == 1){
						from[q] = i;
						to[q] = e.to;
						q++;
					}
				}
			}
		}
		int[][] cg = packU(n, from, to);
		boolean[] ved = new boolean[n];
		int[] cy = new int[n];
		List<int[]> cys = new ArrayList<int[]>();
		for(int i = 0;i < n;i++){
			if(!ved[i]){
				ved[i] = true;
				int r = 0;
				cy[r++] = i+1;
				for(int cur = cg[i][0];!ved[cur];){
					ved[cur] = true; cy[r++] = cur+1;
					if(ved[cg[cur][0]]){
						cur = cg[cur][1];
					}else{
						cur = cg[cur][0];
					}
				}
				cys.add(Arrays.copyOf(cy, r));
			}
		}
		out.println(cys.size());
		for(int[] y : cys){
			out.print(y.length);
			for(int v :y){
				out.print(" " + v);
			}
			out.println();
		}
	}
	
	static int[][] packU(int n, int[] from, int[] to) {
		int[][] g = new int[n][];
		int[] p = new int[n];
		for (int f : from)
			p[f]++;
		for (int t : to)
			p[t]++;
		for (int i = 0; i < n; i++)
			g[i] = new int[p[i]];
		for (int i = 0; i < from.length; i++) {
			g[from[i]][--p[from[i]]] = to[i];
			g[to[i]][--p[to[i]]] = from[i];
		}
		return g;
	}
	
	public static class Edge
	{
		public int from, to;
		public int capacity;
		public int flow;
		public Edge complement;
		// public int iniflow;
		
		public Edge(int from, int to, int capacity) {
			this.from = from;
			this.to = to;
			this.capacity = capacity;
		}
	}
	
	public static Edge[][] compileWD(int n, List<Edge> edges)
	{
		Edge[][] g = new Edge[n][];
		// cloning
		for(int i = edges.size()-1;i >= 0;i--){
			Edge origin = edges.get(i);
			Edge clone = new Edge(origin.to, origin.from, origin.capacity);
			clone.flow = origin.capacity;
			clone.complement = origin;
			origin.complement = clone;
			edges.add(clone);
		}
		
		int[] p = new int[n];
		for(Edge e : edges)p[e.from]++;
		for(int i = 0;i < n;i++)g[i] = new Edge[p[i]];
		for(Edge e : edges)g[e.from][--p[e.from]] = e;
		return g;
	}
	
	public static Edge[][] compileWU(int n, List<Edge> edges)
	{
		Edge[][] g = new Edge[n][];
		// cloning
		for(int i = edges.size()-1;i >= 0;i--){
			Edge origin = edges.get(i);
			Edge clone = new Edge(origin.to, origin.from, origin.capacity*2);
			origin.flow = origin.capacity;
			clone.flow = origin.capacity;
			clone.complement = origin;
			origin.complement = clone;
			origin.capacity *= 2;
			edges.add(clone);
		}
		
		int[] p = new int[n];
		for(Edge e : edges)p[e.from]++;
		for(int i = 0;i < n;i++)g[i] = new Edge[p[i]];
		for(Edge e : edges)g[e.from][--p[e.from]] = e;
		return g;
	}	
	
	public static long maximumFlowDinic(Edge[][] g, int source, int sink)
	{
		int n = g.length;
		int[] d = new int[n];
		int[] q = new int[n];
		long ret = 0;
		while(true){
			Arrays.fill(d, -1);
			q[0] = source;
			int r = 1;
			d[source] = 0;
			
			for(int v = 0;v < r;v++){
				int cur = q[v];
				for(Edge ne : g[cur]){
					if(d[ne.to] == -1 && ne.capacity - ne.flow > 0) {
						q[r++] = ne.to;
						d[ne.to] = d[cur] + 1;
					}
				}
			}
			if(d[sink] == -1)break;
			int[] sp = new int[n];
			for(int i = 0;i < n;i++)sp[i] = g[i].length - 1;
			ret += dfsDinic(d, g, sp, source, sink, Long.MAX_VALUE);
		}
		
		return ret;
	}
	
	private static long dfsDinic(int[] d, Edge[][] g, int[] sp, int cur, int sink, long min)
	{
		if(cur == sink)return min;
		long left = min;
		for(int i = sp[cur];i >= 0;i--){
			Edge ne = g[cur][i];
			if(d[ne.to] == d[cur]+1 && ne.capacity - ne.flow > 0){
				long fl = dfsDinic(d, g, sp, ne.to, sink, Math.min(left, ne.capacity - ne.flow));
				if(fl > 0){
					left -= fl;
					ne.flow += fl;
					ne.complement.flow -= fl;
					if(left == 0){
						sp[cur] = i;
						return min;
					}
				}
			}
		}
		sp[cur] = -1;
		return min-left;
	}

	
	public static long[] isp(int n)
	{
		int[] tprimes = {2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61};
		if(n <= 64){
			long ptn = 0;
			for(int p : tprimes)if(p <= n)ptn |= 1L<<p;
			return new long[]{ptn};
		}
		
		long[] isnp = new long[(n+1)/64+1];
		int sup = (n+1)/64+1;
		
		isnp[0] |= 1<<1;
		for(int tp : tprimes){
			long[] ptn = new long[tp];
			for(int i = 0;i < tp<<6;i+=tp)ptn[i>>>6] |= 1L<<i;
			for(int j = 0;j < sup;j += tp){
				for(int i = 0;i < tp && i+j < sup;i++){
					isnp[j+i] |= ptn[i];
				}
			}
		}
		
		final int[] magic = {0, 1, 2, 53, 3, 7, 54, 27, 4, 38, 41, 8, 34, 55, 48, 28, 62, 5, 39, 46, 44, 42, 22, 9, 24, 35, 59, 56, 49, 18, 29, 11, 63, 52, 6, 26, 37, 40, 33, 47, 61, 45, 43, 21, 23, 58, 17, 10, 51, 25, 36, 32,
	              60, 20, 57, 16, 50, 31, 19, 15, 30, 14, 13, 12};
		for(int i = 0;i < sup;i++){
			for(long j = ~isnp[i];j != 0;j &= j-1){
				int p = i<<6|magic[(int)((j&-j)*0x022fdd63cc95386dL>>>58)];
				if((long)p*p > n)break;
				for(int q = p*p;q <= n;q += p)isnp[q>>6] |= 1L<<q;
			}
		}
		
		for(int i = 0;i < isnp.length;i++)isnp[i] = ~isnp[i];
		for(int tp : tprimes)isnp[0] |= 1L<<tp;
		isnp[isnp.length-1] &= (1L<<n+1)-1;
		
		return isnp;
	}
	
	void run() throws Exception
	{
		is = oj ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);
		
		long s = System.currentTimeMillis();
		solve();
		out.flush();
		tr(System.currentTimeMillis()-s+"ms");
	}
	
	public static void main(String[] args) throws Exception { new C().run(); }
	
	private byte[] inbuf = new byte[1024];
	private int lenbuf = 0, ptrbuf = 0;
	
	private int readByte()
	{
		if(lenbuf == -1)throw new InputMismatchException();
		if(ptrbuf >= lenbuf){
			ptrbuf = 0;
			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
			if(lenbuf <= 0)return -1;
		}
		return inbuf[ptrbuf++];
	}
	
	private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
	private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
	
	private double nd() { return Double.parseDouble(ns()); }
	private char nc() { return (char)skip(); }
	
	private String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	
	private char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while(p < n && !(isSpaceChar(b))){
			buf[p++] = (char)b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}
	
	private char[][] nm(int n, int m)
	{
		char[][] map = new char[n][];
		for(int i = 0;i < n;i++)map[i] = ns(m);
		return map;
	}
	
	private int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}
	
	private int ni()
	{
		int num = 0, b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private boolean oj = System.getProperty("ONLINE_JUDGE") != null;
	private void tr(Object... o) { if(!oj)System.out.println(Arrays.deepToString(o)); }
}