Num = 10 ** 9 + 7
N, M = map(int, input().split())
danger = int(input())
count = 1
l = [1, 1]
for i in range(1, N):
  if i == danger:
    l[1] = 0
    if count < M:
      danger = int(input())
      count += 1
  l = [l[1] % Num, l[0] + l[1]]
  if l == [0, 0]:
    break
if N == danger:
  l[1] = 0
print(l[1] % Num)