### 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 a1-th, a2-th, a3-th, \ldots, aM-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 ≤ N ≤ 105
• 0 ≤ M ≤ N-1
• 1 ≤ a1 < a2 < ... < aM ≤ N-1

### Input

Input is given from Standard Input in the following format:

N M
a1
a2
.
.
.
aM


### 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.