103452: [Atcoder]ABC345 C - One Time Swap

Problem Statement

You are given a string $S$. Find the number of strings that can result from performing the following operation exactly once.

• Let $N$ be the length of $S$. Choose a pair of integers $(i,j)$ such that $1\leq i<j\leq N$ and swap the $i$-th and $j$-th characters of $S$.

It can be proved that you can always perform it under the constraints of this problem.

Constraints

• $S$ is a string of length between $2$ and $10^6$, inclusive, consisting of lowercase English letters.

Input

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

$S$

Output

Print the number of strings that can result from performing the operation in the problem statement exactly once on $S$.

Sample Input 1

abc

Sample Output 1

3

The length of $S$ is $3$, so $1\leq i<j\leq 3$ is satisfied by three pairs of integers $(i,j)$: $(1,2)$, $(1,3)$, and $(2,3)$.

• Swapping the $1$-st and $2$-nd characters of $S$ results in $S$ being bac.
• Swapping the $1$-st and $3$-rd characters of $S$ results in $S$ being cba.
• Swapping the $2$-nd and $3$-rd characters of $S$ results in $S$ being acb.

Therefore, the operation on abc results in one of the three strings: bac, cba, and acb, so print $3$.

Sample Input 2

aaaaa

Sample Output 2

1

Swapping any two characters results in $S$ remaining aaaaa. Thus, only one string can result from the operation.

问题描述

给定一个字符串$S$。找出执行以下操作恰好一次后可以得到的字符串的数量。

• 令$N$为$S$的长度。选择一对整数$(i,j)$，使得$1\leq i<j\leq N$，并将$S$中的第$i$个字符和第$j$个字符交换。

可以证明，在本问题的约束条件下，你总是可以执行此操作。

约束条件

• $S$是一个长度在$2$到$10^6$之间的字符串，由小写英文字母组成。

输入

输入通过标准输入给出以下格式：

$S$

输出

打印在问题描述中的操作恰好执行一次后，$S$可以得到的字符串的数量。

样例输入1

abc

样例输出1

3

$S$的长度为$3$，因此满足$1\leq i<j\leq 3$的整数对$(i,j)$有三个：$(1,2)$，$(1,3)$和$(2,3)$。

• 将$S$中的第$1$个字符和第$2$个字符交换，得到的结果字符串为$S$为bac。
• 将$S$中的第$1$个字符和第$3$个字符交换，得到的结果字符串为$S$为cba。
• 将$S$中的第$2$个字符和第$3$个字符交换，得到的结果字符串为$S$为acb。

因此，在abc上执行操作可以得到三个字符串之一：bac，cba和acb，因此打印$3$。

样例输入2

aaaaa

样例输出2

1

交换任何两个字符都会使$S$保持为aaaaa。因此，操作只能得到一个字符串。