Masala E

This is the easy version of the problem. The difference between the versions is that in this version, string tt consists of only '0' and '1'. You can hack only if you solved all versions of this problem.

Kamron has a binary string $s$ of length $n$. Kamron can perform the following operation:

• Choose two adjacent blocks of $s$ and swap them.

A block is a maximal $substring∗$ of identical characters. Formally, denote $s[l,r]$ as the substring $s_ls_{l+1}…s_r.$ A block is $s[l,r]$ satisfying:

• $l=1 or s_l≠s_{l-1}.$
• $s_l=s_{l+1}=…=s_r.$
• $r=n or s_r≠s_{r+1}.$

Adjacent blocks are two blocks $s[l_1,r_1]$ and $s[l_2,r_2]$ satisfying $r_1+1=l_2$.

For example, if $s=0001100111$, Kamron can choose the two blocks $s[4,5]$ and $s[6,7]$ and swap them, transforming $s$ into $0000011111$.

Given a string t of length n consisting of '0', '1' and '?', Kamron wants to determine the minimum number of operations required to perform such that for any index $i (1≤i≤n)$, if $t_i≠ '?'$ then $s_i=t_i$. If it is impossible, output $−1$.

∗∗A string a is a substring of a string b if a can be obtained from b by the deletion of several (possibly, zero or all) characters from the beginning and several (possibly, zero or all) characters from the end.

Each test contains multiple test cases. The first line contains the number of test cases $t (1≤t≤10^4)$. The description of the test cases follows.

The first line of each test case contains a string s consisting of '0' and '1'.

The second line of each test case contains a string t consisting of '0' and '1'.

It is guaranteed that the lengths of s and tt are the same.

It is guaranteed that the sum of the length of ss over all test cases will not exceed $4⋅10^5$.

For each test case, output one integer — the minimum number of operations required. If it is impossible, output −1.