import sys
input = sys.stdin.readline
N, K = map(int, input().split())
a = set(map(int, input().split()))
for x in a:
  if (x + 1) in a:
    if x - 8 >= 1:
      print("No")
      exit(0)
  if (x + 3) in a:
    if x - 5 >= 1:
      print("No")
      exit(0)
  if (x + 5) in a:
    if x - 8 >= 1:
      print("No")
      exit(0)
#print(a)
for _ in range(200):
  t = set()
  for i in a:
    for j in a:
      if j - i == 1 and (i - 3 > 0): t.add(i - 3)
      if j - i == 3 and (i - 2 > 0): t.add(i - 2)
      if j - i == 5 and (i - 1 > 0): t.add(i - 1)
  if 1 in t:
    print("No")
    exit(0)
  a |= t
for x in a:
  if (x + 1) in a:
    if x - 8 >= 1:
      print("No")
      exit(0)
  if (x + 3) in a:
    if x - 5 >= 1:
      print("No")
      exit(0)
  if (x + 5) in a:
    if x - 8 >= 1:
      print("No")
      exit(0)
sa = sorted(a)
#print(sa)
for i in range(len(sa)):
  if i + 3 >= len(sa): continue
  if sa[i + 3] - sa[i] == 3:
    print("No")
    exit(0)
if 1 in a: print("No")
else: print("Yes")