import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		int k = sc.nextInt();
		TreeSet<Long> out = new TreeSet<>();
		for (int i = 0; i < k; i++) {
		    out.add(sc.nextLong());
		}
		Long current = Long.MAX_VALUE;
		while ((current = out.lower(current)) != null) {
		    int count = 0;
		    long target = current - 4;
		    if (target > 0 && out.contains(target + 3)) {
		        out.add(target);
		        count++;
		    }
		    target = current - 5;
		    if (target > 0 && out.contains(target + 2)) {
		        out.add(target);
		        count++;
		    }
		    target = current - 6;
		    if (target > 0 && out.contains(target + 1)) {
		        out.add(target);
		        count++;
		    }
		    if (count >= 3 || out.contains(1L)) {
		        System.out.println("No");
		        return;
		    }
		}
		System.out.println("Yes");
   }
}