n, k = map(int, input().split())
A = list(map(int, input().split()))
Aset = set(A)

for i in range(k - 1, -1, -1):
    for j in range(A[i], A[i] - 1001, -1):
        if j < 1:
            break
        if (j + 1 in Aset and j + 6 in Aset) or\
           (j + 2 in Aset and j + 5 in Aset) or\
           (j + 3 in Aset and j + 4 in Aset):
            Aset.add(j)
        if 1 in Aset:
            print("No")
            exit()
        if all(k in Aset for k in range(j, j + 7)):
            print("No")
            exit()
print("Yes")