Two strings s1 and s2 are considered $k$ similar (for some non negative integer $k$) if s1 can be transformed into s2 by swapping the positions of two characters exactly $k$ times.

Given two anagrams s1 and s2, return the minimum value of $k$ for which s1 and s2 are $k$ similar.

Constraints:

• $1 \leq$ s1.length $\leq 20$

• s2.length $=$ s1.length

• s1 and s2 contain only lowercase English letters from the set {'a', 'b', 'c', 'd', 'e', 'f'}.

• s2 is an anagram of s1.

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