import java.util.ArrayList;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		sc.close();
		ArrayList<Integer> primes = new ArrayList<>();
		primes.add(2);
		for (int i = 1; 2 * i + 1 <= Math.sqrt(N + 100); i++) {
			int n = 2 * i + 1;
			boolean isPrime = true;
			for (Integer integer : primes) {
				if (n % integer == 0) {
					isPrime = false;
					break;
				}
			}
			if (isPrime) {
				primes.add(n);
			}
		}
		for (int i = N - 100; i <= N + 100; i++) {
			for (Integer integer : primes) {
				if (i % integer == 0 && i / integer != 1) {
					System.out.println(i);
					return;
				}
			}
		}
	}
}