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Score : $150$ points

问题陈述

如果一个字符串 $T$ 满足以下三个条件，则称其为 1122字符串：

• $\lvert T \rvert$ 是偶数。这里，$\lvert T \rvert$ 表示 $T$ 的长度。
• 对于每个整数 $i$，满足 $1\leq i\leq \frac{|T|}{2}$，$T$ 中的第 $(2i-1)$ 个和第 $2i$ 个字符是相同的。
• $T$ 中的每个字符恰好出现零次或两次。也就是说，$T$ 中包含的每个字符在 $T$ 中恰好出现两次。

给定一个由小写英文字母组成的字符串 $S$，请打印 Yes 如果 $S$ 是一个 1122 字符串，否则打印 No。

以上为大语言模型 kimi 翻译，仅供参考。

Problem Statement

A string $T$ is called a 1122 string if and only if it satisfies all of the following three conditions:

• $\lvert T \rvert$ is even. Here, $\lvert T \rvert$ denotes the length of $T$.
• For each integer $i$ satisfying $1\leq i\leq \frac{|T|}{2}$, the $(2i-1)$-th and $2i$-th characters of $T$ are equal.
• Each character appears in $T$ exactly zero or two times. That is, every character contained in $T$ appears exactly twice in $T$.

Given a string $S$ consisting of lowercase English letters, print Yes if $S$ is a 1122 string, and No otherwise.

Constraints

• $S$ is a string of length between $1$ and $100$, inclusive, consisting of lowercase English letters.

Input

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

$S$

Output

If $S$ is a 1122 string, print Yes; otherwise, print No.

Sample Input 1

aabbcc

Sample Output 1

Yes

$S=$aabbcc satisfies all the conditions for a 1122 string, so print Yes.

Sample Input 2

aab

Sample Output 2

No

$S=$aab has an odd length and does not satisfy the first condition, so print No.

Sample Input 3

zzzzzz

Sample Output 3

No

$S=$zzzzzz contains six zs and does not satisfy the third condition, so print No.

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