Given a string A of length N consisting of lowercase English alphabet letters.

You are allowed to perform the following operation on the string A any number of times:

Select a non-empty [subsequence] S of the array $[1,2,3,\ldots,N]$ and any lowercase English alphabet $\alpha$;
Change A_{i} to $\alpha$ for all $i \in$ S.

Find the minimum number of operations required to convert A into a given string B of length N consisting of lowercase English alphabet letters.

------ Input Format ------

• The first line of input contains a single integer T, denoting the number of test cases. The description of T test cases follow.
• The first line of each test case contains an integer N - the length of the string A and B.
• The second line of each test case contains the string A.
• The third line of each test case contains the string B.

------ Output Format ------

For each test case, output the minimum number of operations required to convert string A into string B.

------ Constraints ------

$1 ≤ T ≤ 10^{4}$
$1 ≤ N ≤ 10^{5}$
- Sum of $N$ over all test cases does not exceed $10^{5}$.

----- Sample Input 1 ------
3
2
ab
cd
3
aaa
bab
4
abcd
aaab

----- Sample Output 1 ------
2
1
2

----- explanation 1 ------
Test case 1:
- In the first operation, we can choose $S = \{1\}$ and $\alpha =$ c. After this operation, $A$ will become cb.
- In the second operation, we can choose $S = \{2\}$ and $\alpha =$ d. After this operation, $A$ will become cd.

Test case 2:
- In the first operation, we can choose $S = \{1, 3\}$ and $\alpha =$ b. After this operation, $A$ will become bab.

Test case 3:
- In the first operation, we can choose $S = \{2, 3\}$ and $\alpha =$ a. After this operation, $A$ will become aaad.
- In the second operation, we can choose $S = \{4\}$ and $\alpha =$ b. After this operation, $A$ will become aaab.

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