F. Rotating Substringstime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard outputYou are given two strings s and t, each of length n and consisting of lowercase Latin alphabets. You want to make s equal to t. You can perform the following operation on s any number of times to achieve it —   Choose any substring of s and rotate it clockwise once, that is, if the selected substring is s[l,l+1...r], then it becomes s[r,l,l + 1 ... r - 1]. All the remaining characters of s stay in their position. For example, on rotating the substring [2,4] , string "abcde" becomes "adbce". A string a is a substring of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters from the beginning and several (possibly, zero or all) characters from the end.Find the minimum number of operations required to convert s to t, or determine that it's impossible.InputThe first line of the input contains a single integer t (1\leq t \leq 2000) — the number of test cases. The description of the test cases follows.The first line of each test case contains a single integer n (1\leq n \leq 2000) — the length of the strings. The second and the third lines contain strings s and t respectively.The sum of n over all the test cases does not exceed 2000.OutputFor each test case, output the minimum number of operations to convert s to t. If it is not possible to convert s to t, output -1 instead.ExampleInput
6
1
a
a
2
ab
ba
3
abc
cab
3
abc
cba
4
abab
baba
4
abcc
aabc
Output
0
1
1
2
1
-1
NoteFor the 1-st test case, since s and t are equal, you don't need to apply any operation.For the 2-nd test case, you only need to apply one operation on the entire string ab to convert it to ba.For the 3-rd test case, you only need to apply one operation on the entire string abc to convert it to cab.For the 4-th test case, you need to apply the operation twice: first on the entire string abc to convert it to cab and then on the substring of length 2 beginning at the second character to convert it to cba.For the 5-th test case, you only need to apply one operation on the entire string abab to convert it to baba.For the 6-th test case, it is not possible to convert string s to t.
6
1
a
a
2
ab
ba
3
abc
cab
3
abc
cba
4
abab
baba
4
abcc
aabc

0 1 1 2 1 -1 
['dp', 'strings', '*2600']