Problem: AquaMoon had n strings of length m each. n is an odd number.

When AquaMoon was gone, Cirno tried to pair these n strings together. After making (n-1)/(2) pairs, she found out that there was exactly one string without the pair!

In her rage, she disrupted each pair of strings. For each pair, she selected some positions (at least 1 and at most m) and swapped the letters in the two strings of this pair at the selected positions.

For example, if m = 6 and two strings "abcdef" and "xyzklm" are in one pair and Cirno selected positions 2, 3 and 6 she will swap 'b' with 'y', 'c' with 'z' and 'f' with 'm'. The resulting strings will be "ayzdem" and "xbcklf".

Cirno then stole away the string without pair and shuffled all remaining strings in arbitrary order.

AquaMoon found the remaining n-1 strings in complete disarray. Also, she remembers the initial n strings. She wants to know which string was stolen, but she is not good at programming. Can you help her?

Input

This problem is made as interactive. It means, that your solution will read the input, given by the interactor. But the interactor will give you the full input at the beginning and after that, you should print the answer. So you should solve the problem, like as you solve the usual, non-interactive problem because you won't have any interaction process. The only thing you should not forget is to flush the output buffer, after printing the answer. Otherwise, you can get an "Idleness limit exceeded" verdict. Refer to the [interactive problems guide](https://codeforces.com/blog/entry/45307) for the detailed information about flushing the output buffer.

The input consists of multiple test cases. The first line contains a single integer t (1 ≤ t ≤ 100) — the number of test cases.

The first line of each test case contains two integers n, m (1 ≤ n ≤ 10^5, 1 ≤ m ≤ 10^5) — the number of strings and the length of each string, respectively.

The next n lines each contain a string with length m, describing the original n strings. All string consists of lowercase Latin letters.

The next n-1 lines each contain a string with length m, describing the strings after Cirno exchanged and reordered them.

It is guaranteed that n is odd and that the sum of n ⋅ m over all test cases does not exceed 10^5.

Hack format:

The first line should contain a single integer t. After that t test cases should follow in the following format:

The first line should contain two integers n and m.

The following n lines should contain n strings of length m, describing the original strings.

The following (n-1)/(2) lines should describe the pairs. They should contain, in the following order: the index of the first string i (1 ≤ i ≤ n), the index of the second string j (1 ≤ j ≤ n, i ≠ j), the number of exchanged positions k (1 ≤ k ≤ m), and the list of k positions that are exchanged (k distinct indices from 1 to m in any order).

The final line should contain a permutation of integers from 1 to n, describing the way the strings should be reordered. The strings will be placed in the order indices placed in this permutation, the stolen string index will be ignored.

Output

For each test case print a single line with the stolen string.

Example

Input


3
3 5
aaaaa
bbbbb
ccccc
aaaaa
bbbbb
3 4
aaaa
bbbb
cccc
aabb
bbaa
5 6
abcdef
uuuuuu
kekeke
ekekek
xyzklm
xbcklf
eueueu
ayzdem
ukukuk


Output


ccccc
cccc
kekeke

Note

In the first test case, "aaaaa" and "bbbbb" exchanged all positions, and "ccccc" is the stolen string.

In the second test case, "aaaa" and "bbbb" exchanged two first positions, and "cccc" is the stolen string.

This is the first test in the hack format: 
    
    
      
    3  
    3 5  
    aaaaa  
    bbbbb  
    ccccc  
    1 2 5 1 2 3 4 5  
    2 1 3  
    3 4  
    aaaa  
    bbbb  
    cccc  
    1 2 2 1 2  
    2 1 3  
    5 6  
    abcdef  
    uuuuuu  
    kekeke  
    ekekek  
    xyzklm  
    1 5 3 2 3 6  
    2 4 3 2 4 6  
    5 4 1 2 3  
    

Solution (in JAVA):

Solution:
import static java.lang.Math.max;
import static java.lang.Math.min;
import static java.lang.Math.abs;
import java.util.*;
import java.io.*;
import java.math.*;

/**
 *
 * @Har_Har_Mahadev
 */

/**
 * Main , Solution , Remove Public
 */
public class B {

	public static void process() throws IOException {

		int n = sc.nextInt(),m = sc.nextInt();
		int arr[][] = new int[m][26];
		for(int i = 0; i<n; i++) {
			String str = sc.next();
			for(int j = 0; j<m; j++)arr[j][str.charAt(j)-'a']++;
		}
		for(int i = 1; i<n; i++) {
			String str = sc.next();
			for(int j = 0; j<m; j++)arr[j][str.charAt(j)-'a']--;
		}
		StringBuilder ans = new StringBuilder();
		for(int i = 0; i<m; i++) {
			for(int j =0; j<26; j++) {
				if(arr[i][j] == 1)ans.append((char)(j+'a'));
			}
		}
		System.out.println(ans);
		

	}

	//=============================================================================
	//--------------------------The End---------------------------------
	//=============================================================================
	private static long INF = 2000000000000000000L, M = 1000000007, MM = 998244353;
	private static int N = 0;

	private static void google(int tt) {
		System.out.print("Case #" + (tt) + ": ");
	}

	static FastScanner sc;
	static FastWriter out;

	public static void main(String[] args) throws IOException {
		boolean oj = true;
		if (oj) {
			sc = new FastScanner();
			out = new FastWriter(System.out);
		} else {
			sc = new FastScanner("input.txt");
			out = new FastWriter("output.txt");
		}
		long s = System.currentTimeMillis();
		int t = 1;
		t = sc.nextInt();
		int TTT = 1;
		while (t-- > 0) {
			//			google(TTT++);
			process();
		}
		out.flush();
		//		tr(System.currentTimeMillis()-s+"ms");
	}

	private static boolean oj = System.getProperty("ONLINE_JUDGE") != null;

	private static void tr(Object... o) {
		if (!oj)
			System.err.println(Arrays.deepToString(o));
	}

	static class Pair implements Comparable<Pair> {
		int x, y;

		Pair(int x, int y) {
			this.x = x;
			this.y = y;
		}

		@Override
		public int compareTo(Pair o) {
			return Integer.compare(this.x, o.x);
		}

		/*
		 	@Override
		    public boolean equals(Object o) {
		        if (this == o) return true;
		        if (!(o instanceof Pair)) return false;
		        Pair key = (Pair) o;
		        return x == key.x && y == key.y;
		    }
		 
		    @Override
		    public int hashCode() {
		        int result = x;
		        result = 31 * result + y;
		        return result;
		    }
		*/
	}

	/////////////////////////////////////////////////////////////////////////////////////////////////////////

	static int ceil(int x, int y) {
		return (x % y == 0 ? x / y : (x / y + 1));
	}

	static long ceil(long x, long y) {
		return (x % y == 0 ? x / y : (x / y + 1));
	}

	static long sqrt(long z) {
		long sqz = (long) Math.sqrt(z);
		while (sqz * 1L * sqz < z) {
			sqz++;
		}
		while (sqz * 1L * sqz > z) {
			sqz--;
		}
		return sqz;
	}

	static int log2(int N) {
		int result = (int) (Math.log(N) / Math.log(2));
		return result;
	}

	public static long gcd(long a, long b) {
		if (a > b)
			a = (a + b) - (b = a);
		if (a == 0L)
			return b;
		return gcd(b % a, a);
	}

	public static long lcm(long a, long b) {
		return (a * b) / gcd(a, b);
	}

	public static int lower_bound(int[] arr, int x) {
		int low = 0, high = arr.length - 1, mid = -1;
		int ans = -1;
		while (low <= high) {
			mid = (low + high) / 2;

			if (arr[mid] > x) {
				high = mid - 1;
			} else {
				ans = mid;
				low = mid + 1;
			}
		}

		return ans;
	}

	public static int upper_bound(int[] arr, int x) {
		int low = 0, high = arr.length - 1, mid = -1;
		int ans = arr.length;
		while (low < high) {
			mid = (low + high) / 2;

			if (arr[mid] >= x) {
				ans = mid;
				high = mid - 1;
			} else {
				low = mid + 1;
			}
		}

		return ans;
	}

	static void ruffleSort(int[] a) {
		Random get = new Random();
		for (int i = 0; i < a.length; i++) {
			int r = get.nextInt(a.length);
			int temp = a[i];
			a[i] = a[r];
			a[r] = temp;
		}
		Arrays.sort(a);
	}

	static void ruffleSort(long[] a) {
		Random get = new Random();
		for (int i = 0; i < a.length; i++) {
			int r = get.nextInt(a.length);
			long temp = a[i];
			a[i] = a[r];
			a[r] = temp;
		}
		Arrays.sort(a);
	}

	static void reverseArray(int[] a) {
		int n = a.length;
		int arr[] = new int[n];
		for (int i = 0; i < n; i++)
			arr[i] = a[n - i - 1];
		for (int i = 0; i < n; i++)
			a[i] = arr[i];
	}

	static void reverseArray(long[] a) {
		int n = a.length;
		long arr[] = new long[n];
		for (int i = 0; i < n; i++)
			arr[i] = a[n - i - 1];
		for (int i = 0; i < n; i++)
			a[i] = arr[i];
	}

	//custom multiset (replace with HashMap if needed)
	public static void push(TreeMap<Integer, Integer> map, int k, int v) {
		//map[k] += v;
		if (!map.containsKey(k))
			map.put(k, v);
		else
			map.put(k, map.get(k) + v);
	}

	public static void pull(TreeMap<Integer, Integer> map, int k, int v) {
		//assumes map[k] >= v
		//map[k] -= v
		int lol = map.get(k);
		if (lol == v)
			map.remove(k);
		else
			map.put(k, lol - v);
	}

	// compress Big value to Time Limit
	public static int[] compress(int[] arr) {
		ArrayList<Integer> ls = new ArrayList<Integer>();
		for (int x : arr)
			ls.add(x);
		Collections.sort(ls);
		HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
		int boof = 1; //min value
		for (int x : ls)
			if (!map.containsKey(x))
				map.put(x, boof++);
		int[] brr = new int[arr.length];
		for (int i = 0; i < arr.length; i++)
			brr[i] = map.get(arr[i]);
		return brr;
	}

	// Fast Writer 

	public static class FastWriter {
		private static final int BUF_SIZE = 1 << 13;
		private final byte[] buf = new byte[BUF_SIZE];
		private final OutputStream out;
		private int ptr = 0;

		private FastWriter() {
			out = null;
		}

		public FastWriter(OutputStream os) {
			this.out = os;
		}

		public FastWriter(String path) {
			try {
				this.out = new FileOutputStream(path);
			} catch (FileNotFoundException e) {
				throw new RuntimeException("FastWriter");
			}
		}

		public FastWriter write(byte b) {
			buf[ptr++] = b;
			if (ptr == BUF_SIZE)
				innerflush();
			return this;
		}

		public FastWriter write(char c) {
			return write((byte) c);
		}

		public FastWriter write(char[] s) {
			for (char c : s) {
				buf[ptr++] = (byte) c;
				if (ptr == BUF_SIZE)
					innerflush();
			}
			return this;
		}

		public FastWriter write(String s) {
			s.chars().forEach(c -> {
				buf[ptr++] = (byte) c;
				if (ptr == BUF_SIZE)
					innerflush();
			});
			return this;
		}

		private static int countDigits(int l) {
			if (l >= 1000000000)
				return 10;
			if (l >= 100000000)
				return 9;
			if (l >= 10000000)
				return 8;
			if (l >= 1000000)
				return 7;
			if (l >= 100000)
				return 6;
			if (l >= 10000)
				return 5;
			if (l >= 1000)
				return 4;
			if (l >= 100)
				return 3;
			if (l >= 10)
				return 2;
			return 1;
		}

		public FastWriter write(int x) {
			if (x == Integer.MIN_VALUE) {
				return write((long) x);
			}
			if (ptr + 12 >= BUF_SIZE)
				innerflush();
			if (x < 0) {
				write((byte) '-');
				x = -x;
			}
			int d = countDigits(x);
			for (int i = ptr + d - 1; i >= ptr; i--) {
				buf[i] = (byte) ('0' + x % 10);
				x /= 10;
			}
			ptr += d;
			return this;
		}

		private static int countDigits(long l) {
			if (l >= 1000000000000000000L)
				return 19;
			if (l >= 100000000000000000L)
				return 18;
			if (l >= 10000000000000000L)
				return 17;
			if (l >= 1000000000000000L)
				return 16;
			if (l >= 100000000000000L)
				return 15;
			if (l >= 10000000000000L)
				return 14;
			if (l >= 1000000000000L)
				return 13;
			if (l >= 100000000000L)
				return 12;
			if (l >= 10000000000L)
				return 11;
			if (l >= 1000000000L)
				return 10;
			if (l >= 100000000L)
				return 9;
			if (l >= 10000000L)
				return 8;
			if (l >= 1000000L)
				return 7;
			if (l >= 100000L)
				return 6;
			if (l >= 10000L)
				return 5;
			if (l >= 1000L)
				return 4;
			if (l >= 100L)
				return 3;
			if (l >= 10L)
				return 2;
			return 1;
		}

		public FastWriter write(long x) {
			if (x == Long.MIN_VALUE) {
				return write("" + x);
			}
			if (ptr + 21 >= BUF_SIZE)
				innerflush();
			if (x < 0) {
				write((byte) '-');
				x = -x;
			}
			int d = countDigits(x);
			for (int i = ptr + d - 1; i >= ptr; i--) {
				buf[i] = (byte) ('0' + x % 10);
				x /= 10;
			}
			ptr += d;
			return this;
		}

		public FastWriter write(double x, int precision) {
			if (x < 0) {
				write('-');
				x = -x;
			}
			x += Math.pow(10, -precision) / 2;
			//		if(x < 0){ x = 0; }
			write((long) x).write(".");
			x -= (long) x;
			for (int i = 0; i < precision; i++) {
				x *= 10;
				write((char) ('0' + (int) x));
				x -= (int) x;
			}
			return this;
		}

		public FastWriter writeln(char c) {
			return write(c).writeln();
		}

		public FastWriter writeln(int x) {
			return write(x).writeln();
		}

		public FastWriter writeln(long x) {
			return write(x).writeln();
		}

		public FastWriter writeln(double x, int precision) {
			return write(x, precision).writeln();
		}

		public FastWriter write(int... xs) {
			boolean first = true;
			for (int x : xs) {
				if (!first)
					write(' ');
				first = false;
				write(x);
			}
			return this;
		}

		public FastWriter write(long... xs) {
			boolean first = true;
			for (long x : xs) {
				if (!first)
					write(' ');
				first = false;
				write(x);
			}
			return this;
		}

		public FastWriter writeln() {
			return write((byte) '\n');
		}

		public FastWriter writeln(int... xs) {
			return write(xs).writeln();
		}

		public FastWriter writeln(long... xs) {
			return write(xs).writeln();
		}

		public FastWriter writeln(char[] line) {
			return write(line).writeln();
		}

		public FastWriter writeln(char[]... map) {
			for (char[] line : map)
				write(line).writeln();
			return this;
		}

		public FastWriter writeln(String s) {
			return write(s).writeln();
		}

		private void innerflush() {
			try {
				out.write(buf, 0, ptr);
				ptr = 0;
			} catch (IOException e) {
				throw new RuntimeException("innerflush");
			}
		}

		public void flush() {
			innerflush();
			try {
				out.flush();
			} catch (IOException e) {
				throw new RuntimeException("flush");
			}
		}

		public FastWriter print(byte b) {
			return write(b);
		}

		public FastWriter print(char c) {
			return write(c);
		}

		public FastWriter print(char[] s) {
			return write(s);
		}

		public FastWriter print(String s) {
			return write(s);
		}

		public FastWriter print(int x) {
			return write(x);
		}

		public FastWriter print(long x) {
			return write(x);
		}

		public FastWriter print(double x, int precision) {
			return write(x, precision);
		}

		public FastWriter println(char c) {
			return writeln(c);
		}

		public FastWriter println(int x) {
			return writeln(x);
		}

		public FastWriter println(long x) {
			return writeln(x);
		}

		public FastWriter println(double x, int precision) {
			return writeln(x, precision);
		}

		public FastWriter print(int... xs) {
			return write(xs);
		}

		public FastWriter print(long... xs) {
			return write(xs);
		}

		public FastWriter println(int... xs) {
			return writeln(xs);
		}

		public FastWriter println(long... xs) {
			return writeln(xs);
		}

		public FastWriter println(char[] line) {
			return writeln(line);
		}

		public FastWriter println(char[]... map) {
			return writeln(map);
		}

		public FastWriter println(String s) {
			return writeln(s);
		}

		public FastWriter println() {
			return writeln();
		}
	}

	// Fast Inputs
	static class FastScanner {
		//I don't understand how this works lmao
		private int BS = 1 << 16;
		private char NC = (char) 0;
		private byte[] buf = new byte[BS];
		private int bId = 0, size = 0;
		private char c = NC;
		private double cnt = 1;
		private BufferedInputStream in;

		public FastScanner() {
			in = new BufferedInputStream(System.in, BS);
		}

		public FastScanner(String s) {
			try {
				in = new BufferedInputStream(new FileInputStream(new File(s)), BS);
			} catch (Exception e) {
				in = new BufferedInputStream(System.in, BS);
			}
		}

		private char getChar() {
			while (bId == size) {
				try {
					size = in.read(buf);
				} catch (Exception e) {
					return NC;
				}
				if (size == -1)
					return NC;
				bId = 0;
			}
			return (char) buf[bId++];
		}

		public int nextInt() {
			return (int) nextLong();
		}

		public int[] readArray(int N) {
			int[] res = new int[N];
			for (int i = 0; i < N; i++) {
				res[i] = (int) nextLong();
			}
			return res;
		}

		public long[] readArrayLong(int N) {
			long[] res = new long[N];
			for (int i = 0; i < N; i++) {
				res[i] = nextLong();
			}
			return res;
		}

		public int[][] readArrayMatrix(int N, int M, int Index) {
			if (Index == 0) {
				int[][] res = new int[N][M];
				for (int i = 0; i < N; i++) {
					for (int j = 0; j < M; j++)
						res[i][j] = (int) nextLong();
				}
				return res;
			}
			int[][] res = new int[N][M];
			for (int i = 1; i <= N; i++) {
				for (int j = 1; j <= M; j++)
					res[i][j] = (int) nextLong();
			}
			return res;

		}

		public long[][] readArrayMatrixLong(int N, int M, int Index) {
			if (Index == 0) {
				long[][] res = new long[N][M];
				for (int i = 0; i < N; i++) {
					for (int j = 0; j < M; j++)
						res[i][j] = nextLong();
				}
				return res;
			}
			long[][] res = new long[N][M];
			for (int i = 1; i <= N; i++) {
				for (int j = 1; j <= M; j++)
					res[i][j] = nextLong();
			}
			return res;

		}

		public long nextLong() {
			cnt = 1;
			boolean neg = false;
			if (c == NC)
				c = getChar();
			for (; (c < '0' || c > '9'); c = getChar()) {
				if (c == '-')
					neg = true;
			}
			long res = 0;
			for (; c >= '0' && c <= '9'; c = getChar()) {
				res = (res << 3) + (res << 1) + c - '0';
				cnt *= 10;
			}
			return neg ? -res : res;
		}

		public double nextDouble() {
			double cur = nextLong();
			return c != '.' ? cur : cur + nextLong() / cnt;
		}

		public double[] readArrayDouble(int N) {
			double[] res = new double[N];
			for (int i = 0; i < N; i++) {
				res[i] = nextDouble();
			}
			return res;
		}

		public String next() {
			StringBuilder res = new StringBuilder();
			while (c <= 32)
				c = getChar();
			while (c > 32) {
				res.append(c);
				c = getChar();
			}
			return res.toString();
		}

		public String nextLine() {
			StringBuilder res = new StringBuilder();
			while (c <= 32)
				c = getChar();
			while (c != '\n') {
				res.append(c);
				c = getChar();
			}
			return res.toString();
		}

		public boolean hasNext() {
			if (c > 32)
				return true;
			while (true) {
				c = getChar();
				if (c == NC)
					return false;
				else if (c > 32)
					return true;
			}
		}
	}

}