Increasing Frequency

### 题目描述 给你一个长度为 $n$ 的数列 $a$ ,你可以任意选择一个区间 $[l,r]$, 并给区间每个数加上一个整数 $k$, 求这样一次操作后数列中最多有多少个数等于 $c$. ### 输入格式 第一行两个整数 $n$, $c$ . 第二行 $n$ 个整数 $a_1,a_2,...,a_n$ . $1\le n,c,a_i \le 5\cdot 10^5$ . ### 输出格式 输出一个整数表示答案。

You are given array $ a $ of length $ n $ . You can choose one segment $ [l, r] $ ( $ 1 \le l \le r \le n $ ) and integer value $ k $ (positive, negative or even zero) and change $ a_l, a_{l + 1}, \dots, a_r $ by $ k $ each (i.e. $ a_i := a_i + k $ for each $ l \le i \le r $ ). What is the maximum possible number of elements with value $ c $ that can be obtained after one such operation?

The first line contains two integers $ n $ and $ c $ ( $ 1 \le n \le 5 \cdot 10^5 $ , $ 1 \le c \le 5 \cdot 10^5 $ ) — the length of array and the value $ c $ to obtain. The second line contains $ n $ integers $ a_1, a_2, \dots, a_n $ ( $ 1 \le a_i \le 5 \cdot 10^5 $ ) — array $ a $ .

Print one integer — the maximum possible number of elements with value $ c $ which can be obtained after performing operation described above.

6 9
9 9 9 9 9 9

6

3 2
6 2 6

2

In the first example we can choose any segment and $ k = 0 $ . The array will stay same. In the second example we can choose segment $ [1, 3] $ and $ k = -4 $ . The array will become $ [2, -2, 2] $ .