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.*;
import java.util.*;
import java.util.Map.Entry;

import static java.lang.Math.*;

public class Ans implements Runnable {

	public static void main(String args[]) throws Exception {
		Ans s = new Ans();
		s.run();

	}

	void debug(Object... o) {
		System.out.println(Arrays.deepToString(o));
	}

	InputReader sc = new InputReader(System.in);
	PrintWriter pw = new PrintWriter(System.out);

	public void run() {

		int T = sc.nextInt();
		while (T-- > 0 ) {
			int n = sc.nextInt();
			char[] a = sc.readString().toCharArray();
			char[] b = sc.readString().toCharArray();
			ArrayList<Integer> al = new ArrayList<>();
			int first = 0, last = n-1, xor = 0;
			
			for(int i = n-1; i >= 0 ;i--){
				char a1 = getChar(last, xor, a);
				
				if(a1 != b[i]){
					char f1 = getChar(first, xor, a);

					if(f1 != b[i]){
						al.add(i+1);							
					}else{
						al.add(1);						
						al.add(i+1);
					}
					int temp = first;
					first = last;						
					xor++;
					last = (xor % 2 != 0) ? (temp+1) : (temp-1);

				}else{
					last = (xor % 2 != 0) ? (last+1) : (last-1);
				}
			}
			
			pw.print(al.size());
			for(int ind : al){
				pw.print(" "+ind);
			}
			pw.println();
			
		}

		pw.close();
	}
	
	static char getChar(int ind, int xor, char[] a){
		char c = a[ind];
		if(xor % 2 != 0){		
			c = (c == '1') ? '0' : '1';
		}

		return c;
	}
	
	

	static class InputReader {
		private InputStream stream;
		private byte[] buf = new byte[1024];
		private int curChar;
		private int numChars;
		private SpaceCharFilter filter;

		public InputReader(InputStream stream) {
			this.stream = stream;
		}

		public int read() {
			if (numChars == -1)
				throw new InputMismatchException();

			if (curChar >= numChars) {
				curChar = 0;
				try {
					numChars = stream.read(buf);
				} catch (IOException e) {
					throw new InputMismatchException();
				}

				if (numChars <= 0)
					return -1;
			}
			return buf[curChar++];
		}

		public String nextLine() {
			BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
			String stock = "";
			try {
				stock = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return stock;
		}

		public int nextInt() {
			int c = read();

			while (isSpaceChar(c))
				c = read();

			int sgn = 1;

			if (c == '-') {
				sgn = -1;
				c = read();
			}

			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			} while (!isSpaceChar(c));

			return res * sgn;
		}

		public long nextLong() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			long res = 0;

			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

		public double nextDouble() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			double res = 0;
			while (!isSpaceChar(c) && c != '.') {
				if (c == 'e' || c == 'E')
					return res * Math.pow(10, nextInt());
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			}
			if (c == '.') {
				c = read();
				double m = 1;
				while (!isSpaceChar(c)) {
					if (c == 'e' || c == 'E')
						return res * Math.pow(10, nextInt());
					if (c < '0' || c > '9')
						throw new InputMismatchException();
					m /= 10;
					res += (c - '0') * m;
					c = read();
				}
			}
			return res * sgn;
		}

		public String readString() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isSpaceChar(c));

			return res.toString();
		}

		public boolean isSpaceChar(int c) {
			if (filter != null)
				return filter.isSpaceChar(c);
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}

		public String next() {
			return readString();
		}

		public interface SpaceCharFilter {
			public boolean isSpaceChar(int ch);
		}
	}
}