n,m=map(int,input().split())
a=[]
for i in range(m):
    a.append(int(input()))
count=[0]*(n+2)
count[1]=2
count[0]=1
i=0
s=a.pop(0)
if s==1:
    count[1]=1
    count[0]=0
    if a:
        s=a.pop(0)
if s==2:
    count[1]=0
    if a:
        s=a.pop(0)

while i<n:        
    if (i+2==s-1):
        i=i+1
        if a:
            s=a.pop(0)
    else:
        count[i+2]=(count[i]+count[i+1])%1000000007
        i=i+1
#print(count)
print(count[n-1])
