n,m = map(int,input().split())
a = [int(input()) for _ in range(m)]
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):
  dp[i]=dp[i-2]+dp[i-1]
  if i in a:
    dp[i]=0

print(dp[-1])    