n,m=map(int,input().split())
a=[int(input()) for _ in range(m)]
dp=[0]*(n+1)
ans=0
if n-1 not in a:
    dp[1]=1
if n-2 not in a:
    dp[2]=dp[1]+1
if n>=3:
    for i in range(3,n+1):
        if n-i not in a:
            dp[i]=dp[i-1]+dp[i-2]
        else:
            continue
print(dp[n]%1000000007)