AT_abc456_c.Not Adjacent

You are given a string $S$ consisting of a, b, c.

Find the number of non-empty substrings of $S$ in which no two adjacent characters are the same, modulo $998244353$.

Two substrings are considered distinct if they are taken from different positions, even if they are identical as strings.

What is a substring? A substring of $S$ is a string obtained by deleting zero or more characters from the beginning and zero or more characters from the end of $S$. For example, ab is a substring of abc, but ac is not a substring of abc.

给你一个仅由字符 a、b、c 组成的字符串 $S$。

请计算 $S$ 的非空子串中，满足“任意两个相邻字符均不相同”的子串个数，并对 $998244353$ 取模。

即使两个子串作为字符串完全相同，只要它们在 $S$ 中起始或结束位置不同，就视为不同的子串。

什么是子串？字符串 $S$ 的一个子串是指从 $S$ 的开头删除零个或多个字符、并从 $S$ 的末尾删除零个或多个字符后所得到的字符串。例如，ab 是 abc 的一个子串，但 ac 不是 abc 的子串。

The input is given from Standard Input in the following format:

$S$

输入从标准输入中以如下格式给出：

$S$

Output the answer.

输出答案。

Sample 1 Explanation:
The substrings in which no two adjacent characters are the same are the following six:

• a (from the $1$st to the $1$st character of $S$)
• b (from the $2$nd to the $2$nd character of $S$)
• b (from the $3$rd to the $3$rd character of $S$)
• c (from the $4$th to the $4$th character of $S$)
• ab (from the $1$st to the $2$nd character of $S$)
• bc (from the $3$rd to the $4$th character of $S$)

Note that, as with the $2$nd and $3$rd entries, two substrings are considered distinct if they are taken from different positions, even if they are identical as strings.

Constraints

• $S$ is a string of length between $1$ and $3 \times 10^5$, inclusive, consisting of a, b, c.

样例 1 解释：
满足“任意两个相邻字符均不相同”这一条件的子串共有以下六个：

• a（取自字符串 $S$ 的第 $1$ 个到第 $1$ 个字符）
• b（取自字符串 $S$ 的第 $2$ 个到第 $2$ 个字符）
• b（取自字符串 $S$ 的第 $3$ 个到第 $3$ 个字符）
• c（取自字符串 $S$ 的第 $4$ 个到第 $4$ 个字符）
• ab（取自字符串 $S$ 的第 $1$ 个到第 $2$ 个字符）
• bc（取自字符串 $S$ 的第 $3$ 个到第 $4$ 个字符）

注意：如第 $2$ 项和第 $3$ 项所示，即使两个子串作为字符串完全相同，只要它们在原字符串中起始或结束位置不同，即视为不同的子串。

限制条件

• $S$ 是一个仅由字符 a、b、c 组成的字符串，其长度在 $1$ 到 $3 \times 10^5$（含）之间。