Problem:
Score : 300 points

Problem Statement

There is a staircase with N steps. Takahashi is now standing at the foot of the stairs, that is, on the 0-th step.
He can climb up one or two steps at a time.

However, the treads of the a_1-th, a_2-th, a_3-th, \ldots, a_M-th steps are broken, so it is dangerous to set foot on those steps.

How many are there to climb up to the top step, that is, the N-th step, without setting foot on the broken steps?
Find the count modulo 1\ 000\ 000\ 007.

Constraints

1 \leq N \leq 10^5

0 \leq M \leq N-1

1 \leq a_1 < a_2 < ... < a_M \leq N-1

Input

Input is given from Standard Input in the following format:

N M
a_1
a_2
.
.
.
a_M

Output

Print the number of ways to climb up the stairs under the condition, modulo 1\ 000\ 000\ 007.

Sample Input 1

6 1
3

Sample Output 1

4

There are four ways to climb up the stairs, as follows:

0 \to 1 \to 2 \to 4 \to 5 \to 6

0 \to 1 \to 2 \to 4 \to 6

0 \to 2 \to 4 \to 5 \to 6

0 \to 2 \to 4 \to 6

Sample Input 2

10 2
4
5

Sample Output 2

0

There may be no way to climb up the stairs without setting foot on the broken steps.

Sample Input 3

100 5
1
23
45
67
89

Sample Output 3

608200469

Be sure to print the count modulo 1\ 000\ 000\ 007.

Solution in PyPy3 (2.4.0) (judge verdict: Wrong Answer)

ini=input().split()
ini=[int(i) for i in ini]
N=ini[0]
M=ini[1]

a=[0]
for i in range(M):
    a.append(int(input()))
a.append(N)

#print(a)
ans=1
def fib(n):
    
    atai = 1
    atai2 = 2
   # global atai,atai2
    if n==1:
        atai2=1
        return atai2
    if n==2:
        atai2=2
        return atai2
    else:
        for i in range(1,n):
            temp=atai2
            atai2=atai+temp
            atai=temp
        return atai2
#print(N,M)
for i in range(M+1):
    b=a[i+1]-a[i]-1
    # if i==M:
    #     ans=ans*fib(N-a[i]-1)
    #     print("iff",ans,fib(N-a[i]-1))
    if b==0 and a[1]!=1:
        ans=0
        break
    if b>0:
        ans=ans*fib(b)
#        if ans>1000000007:
        ans=ans % 1000000007
#        print("if",ans,fib(b))
#        print(ans,fib(b),c[i])

ans=ans % 1000000007
print(ans)