String Transformation

A good string is defined as follows.

1. ab is a good string.
2. If a string $S$ is good, then $aSb$, obtained by putting a in front of $S$ and b after it, is also good.
3. If strings $S$ and $T$ are good, then their concatenation $ST$ is also good.

You are given two good strings $A$ and $B$. Using only the operation that swaps two adjacent characters, you want to turn $A$ into $B$. Every string that appears while you do this must also be a good string. Write a program that finds the smallest number of operations needed.

For example, let $A$ be aabbabab and $B$ be aaaabbbb. Five operations turn $A$ into $B$. The brackets mark the two characters swapped at that step.

aabba[ba]b → aab[ba]abb → aaba[ba]bb → aa[ba]abbb → aaa[ba]bbb → aaaabbbb

The first line contains the number of test cases $T$.

Each of the next lines holds one test case: the strings $A$ and $B$, separated by a space. $A$ and $B$ are good strings, and the length of each is between 2 and 100,000.

For each test case, print on its own line the smallest number of operations needed to turn $A$ into $B$. Print -1 if the change is impossible.