Statement

After struggling and failing many times, Ujan decided to try to clean up his house again. He decided to get his strings in order first.

Ujan has two distinct strings $s$ and $t$ of length $n$ consisting of only of lowercase English characters. He wants to make them equal. Since Ujan is lazy, he will perform the following operation exactly once: he takes two positions $i$ and $j$ ( $1 \le i,j \le n$ , the values $i$ and $j$ can be equal or different), and swaps the characters $s_i$ and $t_j$ . Can he succeed?

Note that he has to perform this operation exactly once. He has to perform this operation.

Format

Input

The first line contains a single integer $k$ ( $1 \leq k \leq 10$ ), the number of test cases.

For each of the test cases, the first line contains a single integer $n$ ( $2 \leq n \leq 10^4$ ), the length of the strings $s$ and $t$ .

Each of the next two lines contains the strings $s$ and $t$ , each having length exactly $n$ . The strings consist only of lowercase English letters. It is guaranteed that strings are different.

Output

For each test case, output "Yes" if Ujan can make the two strings equal and "No" otherwise.

Sample

4
5
souse
houhe
3
cat
dog
2
aa
az
3
abc
bca

Yes
No
No
No