n, m = map(int, input().split())
a = []
for i in range(m):
  a.append(int(input()))
ans = 0
flag = 0
  
#フィボナッチ数列の初期値を調節
dp = [0] * (n+1)
dp[0] = 1
if 1 in a:
  dp[1] = 0
else:
  dp[1] = 1
  
for i in range(2, n+1):
  if dp[i-2] == 0 and dp[i-1] == 0:
    ans = 0
    flag = 1
    break
  elif i in a:
    continue
  else:
    dp[i] = dp[i-1] + dp[i-2]
if flag == 0:
  ans = dp[n]
print(ans)
    