MOD = (10 ** 17) + 7
n, m = map(int, input().split())
x = list(map(int, input().split()))

cost = [0 for _ in range(n)]
cost[0] = 1

def areba(i, j):
	if i < j:
		return 0
	else:
		return cost[i - j]

for i in range(1, n):
	for j in x:
		cost[i] = (cost[i] + areba(i, j)) % MOD

print(cost[-1])