Description

Input

The first line contains a single integer $t$ ($1\le t\le 1000$)  — the number of test cases. Next $3t$ lines contain descriptions of test cases.

The first line of each test case contains a single integer $n$ ($1\le n\le 1000$)  — the length of the binary strings.

The next two lines contain two binary strings $a$ and $b$ of length $n$.

It is guaranteed that the sum of $n$ across all test cases does not exceed $1000$.

Output

For each test case, output an integer $k$ ($0\le k\le 3n$), followed by $k$ integers $p_1,\ldots,p_k$ ($1\le p_i\le n$). Here $k$ is the number of operations you use and $p_i$ is the length of the prefix you flip in the $i$-th operation.

5
2
01
10
5
01011
11100
2
01
01
10
0110011011
1000110100
1
0
1

3 1 2 1
6 5 2 5 3 1 2
0
9 4 1 2 10 4 1 2 1 5
1 1

Note

In the first test case, we have $01\to 11\to 00\to 10$.

In the second test case, we have $01011\to 00101\to 11101\to 01000\to 10100\to 00100\to 11100$.

In the third test case, the strings are already the same. Another solution is to flip the prefix of length $2$, which will leave $a$ unchanged.