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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Collection;
import java.util.InputMismatchException;
import java.io.IOException;
import java.util.NoSuchElementException;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        PrefixFlip solver = new PrefixFlip();
        solver.solve(1, in, out);
        out.close();
    }

    static class PrefixFlip {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int tt = in.nextInt();
            while (tt-- > 0) {
                int n = in.nextInt();
                char[] a = in.nextString(n);
                char[] b = in.nextString(n);
                for (int i = 0; i < n; i++) {
                    a[i] -= '0';
                    b[i] -= '0';
                }

                EzIntArrayList fixA = new EzIntArrayList();
                int pref = a[0];
                for (int i = 0; i + 1 < n; i++) {
                    if (a[i] != a[i + 1]) {
                        fixA.add(i);
                        pref = a[i + 1];
                    }
                }

                if (pref == 1) {
                    fixA.add(n - 1);
                }

                EzIntArrayList fixB = new EzIntArrayList();
                pref = b[0];
                for (int i = 0; i + 1 < n; i++) {
                    if (b[i] != b[i + 1]) {
                        fixB.add(i);
                        pref = b[i + 1];
                    }
                }

                if (pref == 1) {
                    fixB.add(n - 1);
                }

                fixB.reverse();
                for (int i = 0; i < fixB.size(); i++) {
                    fixA.add(fixB.get(i));
                }

                out.print(fixA.size() + " ");
                for (int i = 0; i < fixA.size(); i++) {
                    out.print(fixA.get(i) + 1 + " ");
                }
                out.println();
            }
        }

    }

    static interface EzIntList extends EzIntCollection {
        int size();

        EzIntIterator iterator();

        boolean equals(Object object);

        int hashCode();

        String toString();

    }

    static interface EzIntCollection {
        int size();

        EzIntIterator iterator();

        boolean equals(Object object);

        int hashCode();

        String toString();

    }

    static class EzIntArrayList implements EzIntList, EzIntStack {
        private static final int DEFAULT_CAPACITY = 10;
        private static final double ENLARGE_SCALE = 2.0;
        private static final int HASHCODE_INITIAL_VALUE = 0x811c9dc5;
        private static final int HASHCODE_MULTIPLIER = 0x01000193;
        private int[] array;
        private int size;

        public EzIntArrayList() {
            this(DEFAULT_CAPACITY);
        }

        public EzIntArrayList(int capacity) {
            if (capacity < 0) {
                throw new IllegalArgumentException("Capacity must be non-negative");
            }
            array = new int[capacity];
            size = 0;
        }

        public EzIntArrayList(EzIntCollection collection) {
            size = collection.size();
            array = new int[size];
            int i = 0;
            for (EzIntIterator iterator = collection.iterator(); iterator.hasNext(); ) {
                array[i++] = iterator.next();
            }
        }

        public EzIntArrayList(int[] srcArray) {
            size = srcArray.length;
            array = new int[size];
            System.arraycopy(srcArray, 0, array, 0, size);
        }

        public EzIntArrayList(Collection<Integer> javaCollection) {
            size = javaCollection.size();
            array = new int[size];
            int i = 0;
            for (int element : javaCollection) {
                array[i++] = element;
            }
        }

        public int size() {
            return size;
        }

        public EzIntIterator iterator() {
            return new EzIntArrayListIterator();
        }

        public boolean add(int element) {
            if (size == array.length) {
                enlarge();
            }
            array[size++] = element;
            return true;
        }

        public int get(int index) {
            if (index < 0 || index >= size) {
                throw new IndexOutOfBoundsException("Index " + index + " is out of range, size = " + size);
            }
            return array[index];
        }

        private void enlarge() {
            int newSize = Math.max(size + 1, (int) (size * ENLARGE_SCALE));
            int[] newArray = new int[newSize];
            System.arraycopy(array, 0, newArray, 0, size);
            array = newArray;
        }

        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            EzIntArrayList that = (EzIntArrayList) o;

            if (size != that.size) {
                return false;
            }
            for (int i = 0; i < size; i++) {
                if (array[i] != that.array[i]) {
                    return false;
                }
            }
            return true;
        }

        public int hashCode() {
            int hash = HASHCODE_INITIAL_VALUE;
            for (int i = 0; i < size; i++) {
                hash = (hash ^ PrimitiveHashCalculator.getHash(array[i])) * HASHCODE_MULTIPLIER;
            }
            return hash;
        }

        public String toString() {
            StringBuilder sb = new StringBuilder();
            sb.append('[');
            for (int i = 0; i < size; i++) {
                sb.append(array[i]);
                if (i < size - 1) {
                    sb.append(", ");
                }
            }
            sb.append(']');
            return sb.toString();
        }

        public void reverse() {
            reverse(0, size);
        }

        public void reverse(int left, int right) {
            if (left > right || right > size) {
                throw new IllegalArgumentException(
                        "Incorrect range [" + left + ", " + right + ") was specified for reversing, length = " + size);
            }
            for (int i = left, j = right - 1; i < j; i++, j--) {
                int temp = array[i];
                array[i] = array[j];
                array[j] = temp;
            }
        }

        private class EzIntArrayListIterator implements EzIntIterator {
            private int curIndex = 0;

            public boolean hasNext() {
                return curIndex < size;
            }

            public int next() {
                if (curIndex == size) {
                    throw new NoSuchElementException("Iterator doesn't have more elements");
                }
                return array[curIndex++];
            }

        }

    }

    static interface EzIntStack extends EzIntCollection {
        int size();

        EzIntIterator iterator();

        boolean equals(Object object);

        int hashCode();

        String toString();

    }

    static final class PrimitiveHashCalculator {
        private PrimitiveHashCalculator() {
        }

        public static int getHash(int x) {
            return x;
        }

    }

    static class InputReader {
        private final InputStream is;
        private final byte[] inbuf = new byte[1024];
        private int lenbuf = 0;
        private int ptrbuf = 0;

        public InputReader(InputStream stream) {
            is = stream;
        }

        private int readByte() {
            if (lenbuf == -1) throw new InputMismatchException();
            if (ptrbuf >= lenbuf) {
                ptrbuf = 0;
                try {
                    lenbuf = is.read(inbuf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (lenbuf <= 0) return -1;
            }
            return inbuf[ptrbuf++];
        }

        private boolean isSpaceChar(int c) {
            return !(c >= 33 && c <= 126);
        }

        private int skip() {
            int b;
            while ((b = readByte()) != -1 && isSpaceChar(b)) ;
            return b;
        }

        public char[] nextString(int n) {
            char[] buf = new char[n];
            int b = skip(), p = 0;
            while (p < n && !(isSpaceChar(b))) {
                buf[p++] = (char) b;
                b = readByte();
            }
            return n == p ? buf : Arrays.copyOf(buf, p);
        }

        public int nextInt() {
            int num = 0, b;
            boolean minus = false;
            while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')) ;
            if (b == '-') {
                minus = true;
                b = readByte();
            }

            while (true) {
                if (b >= '0' && b <= '9') {
                    num = num * 10 + (b - '0');
                } else {
                    return minus ? -num : num;
                }
                b = readByte();
            }
        }

    }

    static interface EzIntIterator {
        boolean hasNext();

        int next();

    }
}

