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.

// Problem: A2. Prefix Flip (Hard Version)
// Contest: Codeforces - Codeforces Round #658 (Div. 1)
// URL: http://codeforces.com/problemset/problem/1381/A2
// Memory Limit: 256 MB
// Time Limit: 1000 ms
// Powered by CP Editor (https://github.com/cpeditor/cpeditor)

import java.io.*;
import java.util.*;

public class Main {
    private static PrintWriter pw = new PrintWriter(System.out);
    private static InputReader sc = new InputReader();
    private static final int intmax = Integer.MAX_VALUE, intmin = Integer.MIN_VALUE;

    static class Pair{
        int first, second;
        Pair(int first, int second){
            this.first = first;
            this.second = second;
        }
    }

    static class InputReader{
        private static BufferedReader r = new BufferedReader(new InputStreamReader(System.in));
        private static StringTokenizer tk;

        private void next()throws IOException{
            if(tk == null || !tk.hasMoreTokens())   
                tk = new StringTokenizer(r.readLine());
        }

        private int nextInt()throws IOException{
            next();
            return Integer.parseInt(tk.nextToken());
        }

        private String readString()throws IOException{
            next();
            return tk.nextToken();
        }
    }

    public static void main(String args[])throws IOException{
        int t = sc.nextInt();
        while(t-->0)    solve();
        pw.flush();
        pw.close();
    }

    private static void solve()throws IOException{
		int n = sc.nextInt();
		char a[] = sc.readString().toCharArray(), b[] = sc.readString().toCharArray();
		int[] p = new int[n], q = new int[n];
		
		for(int i=0; i<n; i++){
			p[i] = a[i] - '0';
			q[i] = b[i] - '0';
		}
		
		int start = 0, end = n-1, dir = 1;
		
		ArrayList<Integer> ans = new ArrayList<>();
		
		for(int i=n-1; i>=0; i--){
			int prev;
			
			if(dir == 1)
				prev = p[start];
			else
				prev = 1-p[end];
				
			if(prev == q[i])
				ans.add(1);
				
			ans.add(i+1);
			
			if(dir == 1)
				start++;
			else
				end--;
				
			dir = -1*dir;
		}
		
		pw.print(+ans.size()+" ");
		
		for(Integer z: ans)
			pw.print(+z+" ");
		pw.println();
    }
}