import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Deque;
import java.util.Iterator;
import java.util.List;


public class Main_yukicoder308_1 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Printer pr = new Printer(System.out);

        String N = sc.next();

        if (N.length() <= 2) {
        	int n = Integer.parseInt(N);

        	boolean[] notprime = new boolean[n + 1];
        	notprime[1] = true;
        	for (int i = 2; i * i <= n; i++) {
        		if (!notprime[i]) {
        			for (int j = 2; i * j <= n; j++) {
        				notprime[i * j] = true;
        			}
        		}
        	}

        	for (int w = 2; w <= n; w++) {
        		if (dfs(w, n, notprime, pr)) {
        			pr.println(w);
        			break;
        		}
        	}
        } else {
        	int mod = 0;
        	for (int i = 0; i < N.length(); i++) {
        		mod = (10 * mod + (N.charAt(i) - '0')) % 8;
        	}

        	if (mod != 1) {
        		pr.println(8);
        	} else {
        		if (isPrime(N, 8)) {
        			pr.println(14);
        		} else {
            		pr.println(8);
        		}
        	}
        }

        pr.close();
        sc.close();
    }

	private static boolean isPrime(String N, int sub) {
		if (N.length() < 12) {
			long n = Long.parseLong(N);
			n -= sub;
			boolean prime = (n != 1);
			for (long i = 2; i * i <= n; i++) {
				if (n % i == 0) {
					prime = false;
					break;
				}
			}

			return prime;
		} else {
			BigInteger n = new BigInteger(N);
			n = n.subtract(new BigInteger(Integer.toString(sub)));

			return n.isProbablePrime(20);
		}
	}

	private static boolean dfs(int w, int n, boolean[] notprime, Printer pr) {
		int[] d = {w, 1, -1, -w};
		boolean[] used = new boolean[n + 1];

		Deque<Integer> st = new ArrayDeque<Integer>();
		Deque<List<Integer>> rt = new ArrayDeque<List<Integer>>();
		st.push(1);
		rt.push(new ArrayList<Integer>());
		used[1] = true;
		while (!st.isEmpty()) {
			int e = st.pop();
			List<Integer> tmprt = rt.pop();

			for (int i = 0; i < d.length; i++) {
				int tmp = e + d[i];

				if (tmp < 1 || tmp > n) {
					continue;
				}
				if (e % w == 0 && d[i] == 1) {
					continue;
				}
				if (e % w == 1 && d[i] == -1) {
					continue;
				}

				if (tmp == n) {
					tmprt.add(tmp);
//					pr.println(tmprt.toString());

					return true;
				}

				if (!used[tmp] && notprime[tmp]) {
					used[tmp] = true;
					st.push(tmp);
					List<Integer> tt = new ArrayList<Integer>(tmprt);
					tt.add(tmp);
					rt.push(tt);
				}
			}
		}

		return false;
	}

	@SuppressWarnings("unused")
	private static class Scanner {
		BufferedReader br;
		Iterator<String> it;

		Scanner (InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
		}

		String next() throws RuntimeException  {
			try {
				if (it == null || !it.hasNext()) {
					it = Arrays.asList(br.readLine().split(" ")).iterator();
				}
				return it.next();
			} catch (IOException e) {
				throw new IllegalStateException();
			}
		}

		int nextInt() throws RuntimeException {
			return Integer.parseInt(next());
		}

		long nextLong() throws RuntimeException {
			return Long.parseLong(next());
		}

		float nextFloat() throws RuntimeException {
			return Float.parseFloat(next());
		}

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

		void close() {
			try {
				br.close();
			} catch (IOException e) {
//				throw new IllegalStateException();
			}
		}
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}