mod = 10**9+7

def fac(n):
    fac = [1]*(n+1)
    fac[0] = 1
    fac[1] = 1
    for i in range(1,n+1):
        fac[i] = fac[i-1]*i%mod
    return fac

def main():
    n,m=map(int,input().split(' '))
    fact = fac(n)
    check = 0
    pattern = 1
    a = [0]
    a_list = []
    tmp = -1
    for i in range(m):
        an = int(input())
        a.append(an)
    for i in range(m):
        if a[i] !=1:
            a_list.append(a[i+1]-a[i]-1)
    for i in a_list:
        tmp = 0
        for j in range(i):
            tmp +=(fact[(i-j)]/fact[j]/fact[i-2*j])%mod
        pattern *= tmp
        pattern %= mod

    print(int(pattern))

if __name__=='__main__':
    main()