package q8xx;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.Arrays;
import java.util.InputMismatchException;

public class Q840_2 {
	InputStream is;
	PrintWriter out;
	String INPUT = "";
	
	void solve()
	{
		String N = ns();
		if(N.length() <= 2){
			int n = Integer.parseInt(N);
			if(n == 4 || n == 6 || n == 12 || n == 14 || n == 20 || n == 24){
				out.println(n-1);
				return;
			}
			if(n == 21 || n == 25){
				out.println(n-2);
				return;
			}
		}
		
		if(N.length() <= 3){
			int n = Integer.parseInt(N);
			long[] isp = isp(1005);
			for(int w = 1;w <= n;w++){
				if(check(n, w, isp)){
					out.println(w);
					return;
				}
			}
		}
		
		// 8*3*5*7
		int Z = 840;
		BigInteger bn = new BigInteger(N);
		int mt = bn.mod(BigInteger.valueOf(Z)).intValue();
		if(mt == 0)mt += Z;
		BigInteger base = bn.divide(BigInteger.valueOf(Z)).multiply(BigInteger.valueOf(Z));
		if(mt == Z)base = base.subtract(BigInteger.valueOf(Z));
		
		boolean[] ok = new boolean[Z+1];
		for(int num = 1;num <= Z;num++){
			if(num > mt){
				ok[num] = false;
			}else if(num == mt){
				ok[num] = true;
			}else if(num % 3 == 0 || num % 5 == 0 || num % 2 == 0 || num % 7 == 0){
				ok[num] = true;
			}else{
				BigInteger x = base.add(BigInteger.valueOf(num));
				if(x.isProbablePrime(30)){
					ok[num] = false;
				}else{
					ok[num] = true;
				}
			}
		}
		out.println(check(mt, 8, ok) ? 8 : 14);
	}
	
	static boolean check(int n, int w, boolean[] ok)
	{
		DJSet ds = new DJSet(n+1);
		for(int j = 1;j <= n;j++){
			if(j+1 <= n && j%w != 0 && ok[j] && ok[j+1]){
				ds.union(j, j+1);
			}
			if(j+w <= n && ok[j] && ok[j+w]){
				ds.union(j, j+w);
			}
		}
		for(int i = 1;i <= w;i++){
			if(ok[i] && ds.equiv(i, n))return true;
		}
		return false;
	}
	
	static boolean check(int n, int w, long[] isp)
	{
		DJSet ds = new DJSet(n+1);
		for(int j = 1;j <= n;j++){
			if(j+1 <= n && j%w != 0 && isp[j>>>6]<<~j>=0 && isp[j+1>>>6]<<~(j+1)>=0){
				ds.union(j, j+1);
			}
			if(j+w <= n && isp[j>>>6]<<~j>=0 && isp[j+w>>>6]<<~(j+w)>=0){
				ds.union(j, j+w);
			}
		}
		return ds.equiv(1, n);
	}
	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};
		out:
		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 out;
				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;
	}

	
	public static class DJSet {
		public int[] upper;

		public DJSet(int n) {
			upper = new int[n];
			Arrays.fill(upper, -1);
		}

		public int root(int x) {
			return upper[x] < 0 ? x : (upper[x] = root(upper[x]));
		}

		public boolean equiv(int x, int y) {
			return root(x) == root(y);
		}

		public boolean union(int x, int y) {
			x = root(x);
			y = root(y);
			if (x != y) {
				if (upper[y] < upper[x]) {
					int d = x;
					x = y;
					y = d;
				}
				upper[x] += upper[y];
				upper[y] = x;
			}
			return x == y;
		}

		public int count() {
			int ct = 0;
			for (int u : upper)
				if (u < 0)
					ct++;
			return ct;
		}
	}
	
	void run() throws Exception
	{
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);
		
		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
//		Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){
//			@Override
//			public void run() {
//				long s = System.currentTimeMillis();
//				solve();
//				out.flush();
//				if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
//			}
//		};
//		t.start();
//		t.join();
	}
	
	public static void main(String[] args) throws Exception { new Q840_2().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 int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}
	
	private long[] nal(int n)
	{
		long[] a = new long[n];
		for(int i = 0;i < n;i++)a[i] = nl();
		return a;
	}
	
	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[][] nmi(int n, int m) {
		int[][] map = new int[n][];
		for(int i = 0;i < n;i++)map[i] = na(m);
		return map;
	}
	
	private int ni() { return (int)nl(); }
	
	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 static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); }
}