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 JAVA):

Solution:

import java.util.*;
import java.lang.*;
import java.io.*;   
import java.math.*;
public class Prac{     
    static class InputReader { 
        private final InputStream stream;
        private final byte[] buf = new byte[8192];
        private int curChar, snumChars;
        public InputReader(InputStream st) {
            this.stream = st;
        } 
        public int read() {
            if (snumChars == -1)
                throw new InputMismatchException();
            if (curChar >= snumChars) {
                curChar = 0;
                try {
                    snumChars = stream.read(buf);
                } 
                catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (snumChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }
        public int ni() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        } 
        public long nl() {
            int c = read();
            while (isSpaceChar(c)) {
            c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        } 
        public int[] nia(int n) {
            int a[] = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = ni();
            }
            return a;
        } 
        public int[] nia1(int n) {
            int a[] = new int[n+1];
            for (int i = 1; i <=n; i++) {
                a[i] = ni();
            }
            return a;
        } 
        public long[] nla(int n) {
            long a[] = new long[n];
            for (int i = 0; i < n; i++) {
                a[i] = nl();
            }
            return a;
        } 
        public long[] nla1(int n) {
            long a[] = new long[n+1];
            for (int i = 1; i <= n; i++) {
                a[i] = nl();
            }
            return a;
        } 
        public Long[] nLa(int n) {
            Long a[] = new Long[n];
            for (int i = 0; i < n; i++) {
                a[i] = nl();
            }
            return a;
        } 
        public Long[] nLa1(int n) {
            Long a[] = new Long[n+1];
            for (int i = 1; i <= n; i++) {
                a[i] = nl();
            }
            return a;
        } 
        public Integer[] nIa(int n) {
            Integer a[] = new Integer[n];
            for (int i = 0; i < n; i++) {
                a[i] = ni();
            }
            return a;
        } 
        public Integer[] nIa1(int n) {
            Integer a[] = new Integer[n+1];
            for (int i = 1; i <= n; i++) {
                a[i] = ni();
            }
            return a;
        } 
        public String rs() {
            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 String nextLine() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isEndOfLine(c));
            return res.toString();
        } 
        public boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        private boolean isEndOfLine(int c) {
            return c == '\n' || c == '\r' || c == -1;
        } 
    }
    public static class Key {
        private final int x, y;
        public Key(int x, int y) {
            this.x = x; this.y = y;
        }
        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (!(o instanceof Key)) return false;
            Key key = (Key) o;
            return x == key.x && y == key.y;
        }
        @Override
        public int hashCode() {
            int result = x;
            result = 31 * result + y;
            return result;
        }
    }
    static class Pair implements Comparable<Pair>{
            int x,y;
            Pair(int a,int b){
                    x=a;y=b;
            }
            @Override
            public int compareTo(Pair p) {
                    if(x==p.x) return y-p.y;
                    return x-p.x;
            }
    }
    static void shuffleArray(int temp[]){
        int n = temp.length;
        Random rnd = new Random();
        for(int i=0; i<n; ++i){
            int tmp = temp[i];
            int randomPos = i + rnd.nextInt(n-i);
            temp[i] = temp[randomPos];
            temp[randomPos] = tmp;
        }   
    }
    static PrintWriter w = new PrintWriter(System.out);
    static long mod1=998244353L,mod=1000000007;
    //static int r[]={0,1,0,-1}, c[]={1,0,-1,0};
    
    
    public static void main(String [] args){
        InputReader sc=new InputReader(System.in); 
        int t=sc.ni();
        while(t-->0){
            int n=sc.ni();
            char a1[]=sc.nextLine().toCharArray();
            char a2[]=sc.nextLine().toCharArray();
            int a11[]=new int[n];
            int a22[]=new int[n];
            for(int i=0;i<n;i++){
                a11[i]=a1[i]-'0';
                a22[i]=a2[i]-'0';
            }
            ArrayList<Integer> ans=new ArrayList<>();
            for(int i=0;i<n-1;i++){
                if(a11[i]!=a11[i+1]){
                    ans.add(i);
                }
            }
            for(int i=n-2;i>=0;i--){
                a11[i]=a11[i+1];
            }
            int flip=a11[n-1];
            for(int i=n-1;i>=0;i--){
                if(a22[i]!=flip){
                    ans.add(i);
                    flip^=1;
                }
            }
            w.println(ans.size());
            for(int j:ans)w.print((j+1)+" ");
            w.println();
        }
        w.close();
    }
}