**Compilation/Execution Result:**

Given two strings S and T, find length of the shortest subsequence in S which is not a subsequence in T. If no such subsequence is possible, return -1. A subsequence is a sequence that appears in the same relative order, but not necessarily contiguous. A string of length n has different possible subsequences.

**Input:**

The first line of input contains an integer T denoting the number of test cases. Then T test cases follow. The first line of each test case contains integers M and N where M denotes the length of first string and N denotes the length of second string.

The second line of each test case contains the two string S and T. Both string are comprised only of lower case alphabets.

**Output:**

Output the length of the shortest uncommon subsequence for each test case in a new line. If no such sub sequence is possible print -1.

**Constraints:**

1<= T <=100

1<= N,M <=500

**Example:**

**Input:**

1

5 5

babab babba

**Output:**

3

Author: sujnesh

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