Make It Increasing

题意翻译

给你一个数列 $a$ ,一个集合 $b$ , 对于每个 $b$ 中的元素$x$， $a_x$ 不能修改，其他都可以修改，问最少多少次可以将 $a$ 修改为严格单调递增的。如果不存在，输出 $-1$ 。 $a$ 中的所有元素在任意时刻必须都是整数。

题目描述

You are given an array of $ n $ integers $ a_1 $ , $ a_2 $ , ..., $ a_n $ , and a set $ b $ of $ k $ distinct integers from $ 1 $ to $ n $ . In one operation, you may choose two integers $ i $ and $ x $ ( $ 1 \le i \le n $ , $ x $ can be any integer) and assign $ a_i := x $ . This operation can be done only if $ i $ does not belong to the set $ b $ . Calculate the minimum number of operations you should perform so the array $ a $ is increasing (that is, $ a_1 < a_2 < a_3 < \dots < a_n $ ), or report that it is impossible.

输入输出格式

输入格式

The first line contains two integers $ n $ and $ k $ ( $ 1 \le n \le 5 \cdot 10^5 $ , $ 0 \le k \le n $ ) — the size of the array $ a $ and the set $ b $ , respectively. The second line contains $ n $ integers $ a_1 $ , $ a_2 $ , ..., $ a_n $ ( $ 1 \le a_i \le 10^9 $ ). Then, if $ k \ne 0 $ , the third line follows, containing $ k $ integers $ b_1 $ , $ b_2 $ , ..., $ b_k $ ( $ 1 \le b_1 < b_2 < \dots < b_k \le n $ ). If $ k = 0 $ , this line is skipped.

输出格式

If it is impossible to make the array $ a $ increasing using the given operations, print $ -1 $ . Otherwise, print one integer — the minimum number of operations you have to perform.

输入输出样例

输入样例 #1

7 2
1 2 1 1 3 5 1
3 5

输出样例 #1

4

输入样例 #2

3 3
1 3 2
1 2 3

输出样例 #2

-1

输入样例 #3

5 0
4 3 1 2 3

输出样例 #3

2

输入样例 #4

10 3
1 3 5 6 12 9 8 10 13 15
2 4 9

输出样例 #4

3