N,M=map(int,input().split())
A=[]
for i in range(M):
  A.append(int(input()))
ans=0
MOD=1000000007
dp=[]
for i in range(N-1,0,-1):
  if i in A:
    dp[i]=0
    continue
  dp[i]=dp[i+1]+dp[i+2]
  
ans=dp[0]
ans/=MOD
print(ans)
           
