E - Lucky Numbers /

### 問題文

すべての i = 1, 2, \ldots, N-1 について、A_i + A_{i+1} = S_i が成り立つ。

### 制約

• 2 \leq N \leq 10^5
• 1 \leq M \leq 10
• -10^9 \leq S_i \leq 10^9
• -10^9 \leq X_i \leq 10^9
• X_1 \lt X_2 \lt \cdots \lt X_M
• 入力はすべて整数

### 入力

N M
S_1 S_2 \ldots S_{N-1}
X_1 X_2 \ldots X_M


### 入力例 1

9 2
2 3 3 4 -4 -7 -4 -1
-1 5


### 出力例 1

4


### 入力例 2

20 10
-183260318 206417795 409343217 238245886 138964265 -415224774 -499400499 -313180261 283784093 498751662 668946791 965735441 382033304 177367159 31017484 27914238 757966050 878978971 73210901
-470019195 -379631053 -287722161 -231146414 -84796739 328710269 355719851 416979387 431167199 498905398


### 出力例 2

8


Score : 500 points

### Problem Statement

You are given a sequence of N-1 integers S = (S_1, S_2, \ldots, S_{N-1}), and M distinct integers X_1, X_2, \ldots, X_M, which are called lucky numbers.

A sequence of N integers A = (A_1, A_2, \ldots, A_N) satisfying the following condition is called a good sequence.

A_i + A_{i+1} = S_i holds for every i = 1, 2, \ldots, N-1.

Find the maximum possible number of terms that are lucky numbers in a good sequence A, that is, the maximum possible number of integers i between 1 and N such that A_i \in \lbrace X_1, X_2, \ldots, X_M \rbrace.

### Constraints

• 2 \leq N \leq 10^5
• 1 \leq M \leq 10
• -10^9 \leq S_i \leq 10^9
• -10^9 \leq X_i \leq 10^9
• X_1 \lt X_2 \lt \cdots \lt X_M
• All values in input are integers.

### Input

Input is given from Standard Input in the following format:

N M
S_1 S_2 \ldots S_{N-1}
X_1 X_2 \ldots X_M


### Output

Print the maximum possible number of terms that are lucky numbers in a good sequence A.

### Sample Input 1

9 2
2 3 3 4 -4 -7 -4 -1
-1 5


### Sample Output 1

4


A good sequence A = (3, -1, 4, -1, 5, -9, 2, -6, 5) contains four terms that are lucky numbers: A_2, A_4, A_5, A_9, which is the maximum possible count.

### Sample Input 2

20 10
-183260318 206417795 409343217 238245886 138964265 -415224774 -499400499 -313180261 283784093 498751662 668946791 965735441 382033304 177367159 31017484 27914238 757966050 878978971 73210901
-470019195 -379631053 -287722161 -231146414 -84796739 328710269 355719851 416979387 431167199 498905398


### Sample Output 2

8