This is the easy version of the problem. The difference between the versions is that in this version, string $$$t$$$ consists of only '0' and '1'. You can hack only if you solved all versions of this problem.

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

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

A block is a maximal substring$$$^{\text{∗}}$$$ of identical characters. Formally, denote $$$s[l,r]$$$ as the substring $$$s_l s_{l+1} \ldots s_r$$$. A block is $$$s[l,r]$$$ satisfying:

- $$$l=1$$$ or $$$s_l\not=s_{l-1}$$$.
- $$$s_l=s_{l+1} = \ldots = s_{r}$$$.
- $$$r=n$$$ or $$$s_r\not=s_{r+1}$$$.

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 $$$s=\mathtt{000}\,\mathbf{11}\,\mathbf{00}\,\mathtt{111}$$$, Kevin can choose the two blocks $$$s[4,5]$$$ and $$$s[6,7]$$$ and swap them, transforming $$$s$$$ into $$$\mathtt{000}\,\mathbf{00}\,\mathbf{11}\,\mathtt{111}$$$.

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

Input format:
Each test contains multiple test cases. The first line contains the number of test cases $$$t$$$ ($$$1 \le t \le 10^4$$$). 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 $$$t$$$ are the same.

It is guaranteed that the sum of the length of $$$s$$$ over all test cases will not exceed $$$4\cdot 10^5$$$.
Output format:
For each test case, output one integer — the minimum number of operations required. If it is impossible, output $$$-1$$$.
Example Input 0:
6
0001100111
0000011111
010101
111000
0101
0110
0101
1010
011001
001110
0
1

Example Output 0:
1
3
1
-1
-1
-1

Notes:
In the first test case, the possible way is shown in the statement.

In the second test case, one possible way could be:

- Swap blocks $$$[2, 2], [3, 3]$$$, $$$s$$$ will become $$$\mathtt{001101}$$$.
- Swap blocks $$$[3, 4], [5, 5]$$$, $$$s$$$ will become $$$\mathtt{000111}$$$.
- Swap blocks $$$[1, 3], [4, 6]$$$, $$$s$$$ will become $$$\mathtt{111000}$$$.

Example input:
6
0001100111
0000011111
010101
111000
0101
0110
0101
1010
011001
001110
0
1


Example output:
1
3
1
-1
-1
-1