"""

https://yukicoder.me/problems/no/1242

2個の不可能マスが1つの不可能マスを作る
作るのは、1,3,5距離の不可能マスだけ
4つ連続だと確実にアウト

"""

from sys import stdin
import heapq
import sys

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

q = []
d = {}
for i in A:
    heapq.heappush(q,-1*i)
    d[i] = 1


cnt = 0
last = float("inf")

while len(q) > 0:

    now = -1 * heapq.heappop(q)
    if now < 0:
        break
        
    if now == last-1:
        cnt += 1
    else:
        cnt = 1
    last = now
    
    if cnt >= 4:
        print ("No")
        sys.exit()

    if now+1 in d and now-3 not in d:
        d[now-3] = 1
        heapq.heappush(q,-1*(now-3))
    if now+3 in d and now-2 not in d:
        d[now-2] = 1
        heapq.heappush(q,-1*(now-2))
    if now+5 in d and now-1 not in d:
        d[now-1] = 1
        heapq.heappush(q,-1*(now-1))

#print (d)
if 1 not in d:
    print ("Yes")
else:
    print ("No")