from math import factorial
N,M=list(map(int,input().split()))
dansa=[int(input()) for _ in range(M)]
ans=1
flag=True
if dansa[0]==0:
    print("0")
else:
    if len(dansa)>1:
        for i in range(M-1):
            if dansa[i]+1==dansa[i+1]:
                print("0")
                flag=False
                break
if flag:
    dansa.insert(0,0)
    dansa.append(N)
    for i in range(M+1):
        tmp=dansa[i+1]-dansa[i]-1
        arr=[i for i in range(int(tmp/2)+1)]
        #print("tmp:{}".format(tmp))
        hoge=0
        """
        if tmp%2==0:
            arr=[j*2 for j in range(0,int(tmp/2+1))]
            
        else:
            arr=[j*2+1 for j in range(0,int((tmp+1)/2))]
        """
        #print(arr)
        #if tmp%2==0:
        for k in arr:
            n=tmp-k
            hoge+=factorial(n) / factorial(k) / factorial(n-k)
            
        #print(hoge)
        ans=ans*hoge
        #print(ans)
    print(int(ans%1000000007))
    #print(ans)

