import sys
input = sys.stdin.readline

N,K=map(int,input().split())
A=list(map(int,input().split()))

NG=set(A)

for a in A[::-1]:
    for j in range(a,a-1001,-1):
        if j<1:
            continue
        
        if (j+1 in NG and j+6 in NG) or (j+2 in NG and j+5 in NG) or (j+3 in NG and j+4 in NG):
            NG.add(j)

        if 1 in NG:
            print("No")
            sys.exit()

        if j in NG and j+1 in NG and j+2 in NG and j+3 in NG and j+4 in NG and j+5 in NG and j+6 in NG:
            print("No")
            sys.exit()
        
else:
    print("Yes")