Problem: This is the easy version of the problem. The difference between the versions is the constraint on n and the required number of operations. You can make hacks only if all versions of the problem are solved.

There are two binary strings a and b of length n (a binary string is a string consisting of symbols 0 and 1). In an operation, you select a prefix of a, and simultaneously invert the bits in the prefix (0 changes to 1 and 1 changes to 0) and reverse the order of the bits in the prefix.

For example, if a=001011 and you select the prefix of length 3, it becomes 011011. Then if you select the entire string, it becomes 001001.

Your task is to transform the string a into b in at most 3n operations. It can be proved that it is always possible.

Input

The first line contains a single integer t (1≤ t≤ 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≤ n≤ 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≤ k≤ 3n), followed by k integers p_1,…,p_k (1≤ p_i≤ 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.

Example

Input


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


Output


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→ 11→ 00→ 10.

In the second test case, we have 01011→ 00101→ 11101→ 01000→ 10100→ 00100→ 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.

Solution (in PYTHON3):

Solution:
import sys

input = sys.stdin.readline

_DEBUG = False


def flip(ch):
    return '1' if ch == '0' else '0'


def solve(n, a, b):
    if a == b:
        return [0]
    r = []

    inv_flip_count = 0
    al_idx, ar_idx = 0, n - 1

    for i in range(n - 1, -1, -1):
        if inv_flip_count % 2 == 0:
            a0, ai = a[al_idx], a[ar_idx]
        else:
            a0, ai = flip(a[al_idx]), flip(a[ar_idx])

        if ai != b[i]:
            if a0 != b[i]:
                r.append(i + 1)
            else:
                r.extend([1, i + 1])
            inv_flip_count += 1
            al_idx, ar_idx = ar_idx, al_idx

        if inv_flip_count % 2 == 0:
            ar_idx -= 1
        else:
            ar_idx += 1

    return [len(r)] + r


# assert solve(5, '01011', '11100') == [3, 1, 5, 2]

for _ in range(int(input())):
    n = int(input())
    a = input()
    b = input()

    sys.stdout.write(' '.join(map(str, solve(n, a, b))) + '\n')