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 java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.*;


public class Main {
	
	static int mod = 1000000007;
	
	//--------------------------------- Scanner --------------------------------------//
	
// 	public static class Scanner {
// 	    BufferedReader br;
// 	    StringTokenizer st;
// 	    public Scanner() {
// 	       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;
// 	    }

// 	}
	
	// -------------------------- Print and Flush ------------------------------------ //
	
	public static void print(int[] arr) {
		for(int i=0 ; i<arr.length ; i++) System.out.print(arr[i]+" ");
		System.out.println();
	}
	
	public static void print(int[][] arr) {
		for(int i=0 ; i<arr.length ; i++) {
			for(int j=0 ; j<arr[0].length ; j++) System.out.print(arr[i][j]+" ");
			System.out.println();
		}
	}
	
	public static void print(int res) {
		System.out.println(res);
	}
	
	public static void print(String res) {
		System.out.println(res);
	}
	
	public static void print(int a , int b) {
		System.out.println(a + " " + b);
	}
	
	public static void print(char[] res) {
		for (int i = 0 ; i < res.length ; i++) 
			System.out.print(res[i]);
		System.out.println();
	}
	
	public static void flush() {
		System.out.flush();
	}
	
	// --------------------------- Is Palindrome ------------------------------------- //
	
	public static boolean isPalindrome(String str) {
		for (int i = 0 ; i < str.length() ; i++) { 
			if (str.charAt(i) != str.charAt(str.length() - i - 1))
				return false;
		}
		return true;
	}
	
	//-------------------------------- Pair ------------------------------------------ //
	
	public static class Pair {
		int x;
		int y;
		Pair(int x, int y) {
			this.x = x;
			this.y = y;
		}
		Pair(Pair p) {
			x = p.x;
			y = p.y;
		}
	}
	
	//------------------------------- Comparator ------------------------------------ //
	
	static class cmp implements Comparator<Pair> {
		public int compare(Pair p1 , Pair p2) {
			if (p1.y > p2.y)
				return 1;
			return -1;
		}
	}
	
	// ----------------------------- Tries ------------------------------------------- //
	
	static class Tries {
		char ch = '\u0000';
		int count = 0;
		Tries[] arr = new Tries[26];
		boolean isEnd = false;
		Tries(char ch) {
			this.ch = ch;
		}
		Tries () { }
	}
	static Tries dummy = new Tries(); 
	static int tries_insert(String str) {
		Tries temp = dummy;
		for (int i = 0 ; i < str.length() ; i++) {
			int pos = str.charAt(i) - 'a';
			if (temp.arr[pos] == null) 
				temp.arr[pos] = new Tries(str.charAt(i));
			temp = temp.arr[pos];
		}
		temp.isEnd = true;
		temp.count += 1;
		return temp.count;
	}
	
	// ------------------------- Prime Number (seive) ------------------------------- //
	
	static int len = 10001;
	static int[] prime_number = new int[len];
	static Set<Integer> prime_number_set = new HashSet<>();
	static Set<Long> three_factor_set = new HashSet<>(); 
	static void seive() {
		prime_number[0] = 1;
		prime_number[1] = 1;
		for (int i = 2 ; i < len ; i++) {
			if (prime_number[i] == 0) {
				long val = i;
				prime_number_set.add(i);
				//three_factor_set.add(val * val);
				for (int j = i + i ; j < len ; j+=i) 
					prime_number[j] = 1;
			}
		}
	}
	
	static long[] product = new long[200001];
	static void multiply() {
		product[0] = 1;
		product[1] = 1;
		for (int i = 2 ; i < 200001 ; i++)
			product[i] = (product[i - 1] * i) % mod;
	}
	
	//--------------------------- perfect square ------------------------------------ //
	
	static Set<Integer> perfect_square = new HashSet();
	static void ps(int len) {
		for (int i = 1 ; i <= len ; i++) {
			perfect_square.add(i * i);
		}
	}
	
	
	// ---------------------------------- Sqrt -------------------------------------- //
		
	static long pow(long a , long b , long M) {
		if (b == 0)
			return 1;
		long mid = pow(a , b/2 , M) % M;
		if (b % 2 == 0) 
			return (mid * mid) % M;
		return (((mid * mid) % M) * a) % M;
	}
	
	static long sumDigit(long num) {
		long res = 0;
		while (num > 0) {
			res += num % 10;
			num = num / 10;
		}
		return res;
	}
	
	static long fact(int len , long M) {
		long res = 1;
		for (int i = 1 ; i < len ; i++) {
			res = (res * i) % M;
		}
		return res % M;
	}
	
	// ------------------------------- GCD ---------------------------------------- // 
	
	static long longGcd(long a , long b) {
		if (a > b) 
			longGcd(b , a);
		if (a == 0)
			return b; 
		return longGcd(b % a , a);
	}
    
    static int gcd(int a , int b) {
		if (a > b) 
			gcd(b , a);
		if (a == 0)
			return b; 
		return gcd(b % a , a);
	}
	
	
	// ----------------------------- LOWER BOND ------------------------------------ //
	
	static int upperBond(int[] arr , int target) {
		int st = 0 , end = arr.length - 1 , mid = 0;
		while (st < end) {
			mid = st + ((end - st) >> 1);
			if (arr[mid] < target) 
				st = mid + 1;
			else 
				end = mid;
		}
		return arr[end];
	}
	
	static int lowerBond(int[] arr , int target) {
		int st = 0 , end = arr.length - 1 , mid = 0;
		while (st < end) {
			mid = st + ((end - st) >> 1); 
			if (arr[mid] > target)
				end = mid - 1;
			else 
				st = mid;
		}
		return arr[st];
	}
    
    
    // --------------------------- print YES NO -------------------------------------//
    
    static void py() {
        System.out.println("YES");
    }
    
    static void pn() {
        System.out.println("NO");
    }
	
	
	// -------------------------- Solve --------------------------------------------- //
    static double dfs(double c , double m , double p , double v , double h) {
        
        
        if (c == 0 && m == 0)
           return p * h;
        
        if (c == 0) {
            double c2 = m <= v ? dfs(0 , 0 , p + m , v , h + 1) : dfs(0 , v , p + m - v , v , h + 1);
            return (m * c2) + (p * h);
        }
        
        if (m == 0) {
           double c1 = c <= v ? dfs(0 , 0 , p + c , v , h + 1) : dfs(v , 0 , p + c - v , v , h + 1);
            return (c * c1) + (p * h);
        }
        
        
        //System.out.println(m + ch + " " + m + " " + p);
        double c1 = c <= v ? dfs(0 , m + (c / 2) , p + (c / 2) , v , h + 1) : dfs(v , m + ((c - v) / 2) , p + ((c - v) / 2) , v , h + 1); 
        
        double c2 = m <= v ? dfs(c + (m / 2) , 0 , p + (m / 2) , v , h + 1) : dfs(c + ((m - v) / 2) , v , p + ((m - v) / 2) , v , h + 1);
        
        return  (c * c1) + (c * c2) + (p * h);
    }
    
    static int bs(int[] arr , int target) {
        int st = 0 , end = arr.length , mid = 0;
        
        while (st <= end) {
            mid = st + ((end - st) >> 1);
            
            if (arr[mid] == target)
                return mid;
            else if (arr[mid] < target) 
                st = mid + 1;
            else
                end = mid - 1;
        }
        
        return end;
    }
    
    static void merge(int[] arr , int st , int mid , int end , int[] index) {
        
        int leftSize = mid - st;
        int[] left = new int[leftSize];
        
        for (int i = 0 ; i < leftSize ; i++) {
            left[i] = index[i + st];
        }
        
        int rightSize = end - mid + 1;
        int[] right = new int[rightSize];
        
        
        for (int i = 0 ; i < rightSize ; i++) {
            right[i] = index[i + mid];
        }
        
        int l = 0 , r = 0 , k = st;
        while (l < leftSize && r < rightSize) {
            
            if (arr[left[l]] <= arr[right[r]]) {
                index[k] = left[l];
                k += 1;
                l += 1;
            } else {
                index[k] = right[r];
                k += 1;
                r += 1;
            }
            
        }
        
        while (l < leftSize) {
            index[k] = left[l];    
            k += 1;
            l += 1;
        }
        
        while (r < rightSize) {
            index[k] = right[r];
            k += 1;
            r += 1;
        }
        
    }
    
    
    static void mergeSort(int[] arr , int st , int end , int[] index) {
        
        if (st == end)
            return ;
        
        int mid = st + ((end - st) >> 1);
        
        mergeSort(arr , st , mid , index);
        mergeSort(arr , mid + 1 , end , index);
        
        merge(arr , st , mid + 1 , end , index);
    }
    
    
    
	public static void solve(Scanner s) {
        
	}
    
    public static void B(Scanner s) {
        int n = s.nextInt();
        int m = s.nextInt();
        
        String[] a = new String[n];
        
        for (int i = 0 ; i < n ; i++) 
            a[i] = s.next();
        
        
        String[] b = new String[n - 1];
        
        for (int i = 0 ; i < n - 1 ; i++) 
            b[i] = s.next();
        
        
        
        String res = "";
        
        for (int i = 0 ; i < m ; i++) {
            int[] arr1 = new int[26];
            for (int j = 0 ; j < n ; j++) {
                int val = a[j].charAt(i) - 'a';
                arr1[val] += 1;
            }
            
            int[] arr2 = new int[26];
            
            for (int j = 0 ; j < n - 1 ; j++) {
                int val = b[j].charAt(i) - 'a';
                arr2[val] += 1;
            }
            
            for (int j = 0 ; j < 26 ; j++) {
                //System.out.println(arr1[j] + " " + arr2[j]);
                if (arr1[j] != arr2[j]) {
                    res += (char)('a' + j);
                    break;
                }
            }
        }
        
        System.out.println(res);
        flush();
        
        
    }
    
    public static void C(Scanner s) {
        int n = s.nextInt();
        
        int[] arr1 = new int[n];
        int[] arr2 = new int[n];
        for (int i = 0 ; i < n ; i++) { 
            arr1[i] = s.nextInt();
            arr2[i] = arr1[i];
        }
            
        Arrays.sort(arr1);
        
        Map<Integer , Integer> even = new HashMap<>();
        Map<Integer , Integer> odd = new HashMap<>();
        
        
        for (int i = 0 ; i < n ; i += 2) 
            even.put(arr2[i] , even.getOrDefault(arr2[i] , 0) + 1);
        
        for (int i = 1 ; i < n ; i += 2)
            odd.put(arr2[i] , odd.getOrDefault(arr2[i] , 0) + 1);
        
        for (int i = 0 ; i < n ; i++) {
            if (i % 2 == 0 && even.containsKey(arr1[i])) {
                even.put(arr1[i] , even.get(arr1[i]) - 1);
                if (even.get(arr1[i]) == 0)
                    even.remove(arr1[i]);
            } else if (i % 2 != 0 && odd.containsKey(arr1[i])) {
                odd.put(arr1[i] , odd.get(arr1[i]) - 1);
                if (odd.get(arr1[i]) == 0)
                    odd.remove(arr1[i]);
            } else {
                pn();
                return ;
            }    
        }
         
        py();
    }
	
	
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
//	    PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));
//	    multiply();
//		seive();
//		ps(1000000);
//		prime_number_set.add(1);
        int t = s.nextInt();
//	    s.nextLine();
	    while(t-->0) { 
	    	//A(s);
            B(s);
            //C(s);
            //D(s);
            
        }

	    
//		e(s);
//	    int n      = s.nextInt();        // read input as integer
//	    long k     = s.nextLong();       // read input as long
//	    double d   = s.nextDouble();     // read input as double
//	    String str = s.next();           // read input as String
//	    String str2  = s.nextLine();       // read whole line as String
//	    long result = 3*k;
//	    out.println(result);                    // print via PrintWriter	   
//	    out.close();
	
	}
}