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.
import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.util.Scanner; 
import java.util.StringTokenizer; 
import java.util.*;  
public class Main 
{ 
    static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    } 
  
    public static void main(String[] args) 
    { 
        FastReader sc=new FastReader(); 
        int t=sc.nextInt();
        StringBuilder sb=new StringBuilder();
        while(t-->0)
        {
            int n=sc.nextInt();
            String a=sc.next();
            String b=sc.next();
            ArrayList<Integer> adj=new ArrayList<>();
            int p=0;
            int d1=0;
            int d2=n-1;
            int q=n-1;
            int flip=0;
            boolean rev=false;
            char s1[]=a.toCharArray();
            char s2[]=b.toCharArray();
            for( q=n-1;q>=0;q--)
            {
                if(((s1[p]-'0')+flip)%2==(s2[q]-'0'))
                {
                    adj.add(1);
                    adj.add(q+1);
                    rev=!rev;
                    if(rev)
                    {
                        d1++;
                        p=d2;
                    }
                    else
                    {
                        d2--;
                        p=d1;
                    }
                    flip=1-flip;
                }
                else
                {
                    adj.add(q+1);
                    rev=!rev;
                     if(rev)
                    {
                        d1++;
                        p=d2;
                    }
                    else
                    {
                        d2--;
                        p=d1;
                    }
                    flip=1-flip;
                }
            }
            sb.append((adj.size())+"\n");
            for( int i:adj)
            sb.append(i+" ");
            sb.append("\n");
            
        }
        System.out.println(sb.toString());
	}
}
