Speed Typing

Barbara is a fast typist. To check her typing speed, she takes a speed test in which she must type a string $I$.

While she types, she may press a wrong key. She does not want to lose time fixing mistakes, so she keeps typing with the errors until the test ends. When the test ends, she has produced a string $P$.

Find how many extra letters must be deleted from $P$ to get $I$. Deleting letters from $P$ may not be enough to get $I$, because she may have made a mistake that cannot be undone by deletion. She may also have skipped some letters.

The first line contains the number of test cases $T$. Each test case has two lines. The first line is the string $I$ that the test gave her. The second line is the string $P$ that Barbara typed.

For each test case, print one line in the form Case #x: y. Here $x$ is the test case number starting from 1, and $y$ is the number of extra letters to delete from $P$ to get $I$. If $I$ cannot be obtained by deleting letters from $P$, print IMPOSSIBLE as $y$.

$1≤T≤100$.

Both strings contain only letters from a-z and A-Z.

$1≤|I|,|P|≤10^5$.