def fibonacci(x, y):
  return x + y

n, m = map(int, input().split())
a = []
for i in range(m):
  a.append(int(input()))

for i in range(m-1):
  if a[i+1] - a[i] == 1:
    ans = 0
    flag = 1
    break

dp = [0] * 3
dp[0] = 1
dp[1] = 2
if flag == 0:
  if a[0] == 1:
    dp[0] = 1
    dp[1] = 1
for i in range(n):
  dp[2] 
	
      
print(ans%(10**9+7)) 