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

$S$

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