import numpy as np

K = int(input())
N = int(input())
X = np.array(list(map(int, input().split())))
dp = np.zeros(K, dtype = int)
Y = np.zeros(K, dtype = int)
mod = 10**9 + 7

for x in X:
    if x < K:
        Y[-x] = 1
        dp[x-1] = 1

for j in range(1,K):
    dp[j] += np.dot(Y[-j:], dp[:j])
    dp[j] %= mod

print(dp[-1])