Score : $400$ points

问题描述

你将获得一个字符串 $S$，它是 atcoder 的一个排列。

在该字符串 $S$ 上，你需要执行以下操作零次或多次：

• 选择 $S$ 中的两个相邻字符并交换它们。

找出使 $S$ 等于 atcoder 所需的最少操作次数。

以上为通义千问 qwen-max 翻译，仅供参考。

Problem Statement

You are given a string $S$ that is a permutation of atcoder.
On this string $S$, you will perform the following operation $0$ or more times:

• Choose two adjacent characters of $S$ and swap them.

Find the minimum number of operations required to make $S$ equal atcoder.

Constraints

• $S$ is a string that is a permutation of atcoder

Input

Input is given from Standard Input in the following format:

$S$

Output

Print the answer as an integer.

Sample Input 1

catredo

Sample Output 1

8

You can make $S$ equal atcoder in $8$ operations as follows:
catredo $\rightarrow$ [ac]tredo $\rightarrow$ actre[od] $\rightarrow$ actr[oe]d $\rightarrow$ actro[de] $\rightarrow$ act[or]de $\rightarrow$ acto[dr]e $\rightarrow$ a[tc]odre $\rightarrow$ atcod[er]
This is the minimum number of operations achievable.

Sample Input 2

atcoder

Sample Output 2

0

In this case, the string $S$ is already atcoder.

Sample Input 3

redocta

Sample Output 3

21

update @ 2024/3/10 11:09:23