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.util.*;
import java.io.*;
import java.math.*;


/**
 * @author Naitik
 * 
 */
public class Main

{ 
	 static FastReader sc=new FastReader(); 
	 static long dp[][];
	 static int mod=1000000007;
	 static int max;
	 static long bit[];
	 static long seg[];

	   static PrintWriter out=new PrintWriter(System.out);
	  public static void main(String[] args)
{
		    //CHECK FOR N=1
	       	//CHECK FOR N=1
		   //StringBuffer sb=new StringBuffer("");
		  int ttt=1;
		      ttt =i();
	        outer :while (ttt-- > 0) 
			{
	        	int n=i();
	        	int m=i();
	        	int A[][]=new int[m][26];
	        	for(int i=0;i<n;i++) {
	        		char B[]=s().toCharArray();
	        		for(int j=0;j<m;j++) {
	        			A[j][B[j]-'a']++;
	        		}
	        	}
	        	for(int i=0;i<n-1;i++) {
	        		char B[]=s().toCharArray();
	        		for(int j=0;j<m;j++) {
	        			A[j][B[j]-'a']--;
	        		}
	        	}
	        	StringBuffer sb=new StringBuffer("");
	        	for(int i=0;i<m;i++) {
	        		for(int j=0;j<26;j++) {
	        			if(A[i][j]>0) {
	        				char ch=(char)('a'+j);
	        				sb.append(ch);
	        				break;
	        			}
	        		}
	        	}
	        	System.out.println(sb);
	        	
	        	
	        	
	        }
	        //System.out.println(sb.toString());
		     out.close();
	     
	     
	    //CHECK FOR N=1                    //CHECK FOR M=0
        //CHECK FOR N=1                    //CHECK FOR M=0
       	//CHECK FOR N=1
       	
		        
		     
    }
	 
	  
	  
	  
static class Pair implements Comparable<Pair>
     {
    	 int x;
    	 int y;
    	 Pair(int x,int y){
    		 this.x=x;
    		 this.y=y;
    		 
    	 }
		@Override
		public int compareTo(Pair o) {
			if(this.x>o.x)
				return 1;
			else if(this.x<o.x)
				return -1;
			else {
				if(this.y>o.y)
					return 1;
				else if(this.y<o.y)
					return -1;
				else
					return 0;
			}
		}
//		public int hashCode() 
//		{ 
//			final int temp = 14; 
//			int ans = 1; 
//			ans =x*31+y*13; 
//			return ans; 
//		} 
//		@Override
//		public boolean equals(Object o) 
//		{ 
//			if (this == o) { 
//				return true; 
//			} 
//			if (o == null) { 
//				return false; 
//			} 
//			if (this.getClass() != o.getClass()) { 
//				return false; 
//			} 
//			Pair other = (Pair)o; 
//			if (this.x != other.x || this.y!=other.y) { 
//				return false; 
//			} 
//			return true; 
//		} 	
//		
		/* FOR TREE MAP PAIR USE */
		
//		public int compareTo(Pair o) {
// 			if (x > o.x) {
// 				return 1;
// 			}
// 			if (x < o.x) {
// 				return -1;
// 			}
// 			if (y > o.y) {
// 				return 1;
// 			}
// 			if (y < o.y) {
// 				return -1;
// 			}
// 			return 0;
// 		}
		
     }
//FENWICK TREE
static void update(int i, int x){
	for(; i < bit.length; i += (i&-i))
		bit[i] += x;
}

static int sum(int i){
	int ans = 0;
	for(; i > 0; i -= (i&-i))
		ans += bit[i];
	return ans;
}
//END
//static void add(int v) {
//	if(!map.containsKey(v)) {
//		map.put(v, 1);
//	}
//	else {
//		map.put(v, map.get(v)+1);
//	}
//}
//static void remove(int v) {
//	if(map.containsKey(v)) {
//		map.put(v, map.get(v)-1);
//		if(map.get(v)==0)
//			map.remove(v);
//	}
//}
public static int upper(int A[],int k,int si,int ei)
{
	int l=si;
	int u=ei;
	int ans=-1;
	while(l<=u) {
		int mid=(l+u)/2;
		if(A[mid]<=k) {
			ans=mid;
			l=mid+1;
		}
		else {
			u=mid-1;
		}
	}
	return ans;
}
public static int lower(int A[],int k,int si,int ei)
{
	int l=si;
	int u=ei;
	int ans=-1;
	while(l<=u) {
		int mid=(l+u)/2;
		if(A[mid]<k) {
			l=mid+1;
		}
		else {
			ans=mid;
			u=mid-1;
		}
	}
	return ans;
	
    
}
static int[] copy(int A[]) {
	int B[]=new int[A.length];
	for(int i=0;i<A.length;i++) {
		B[i]=A[i];
	}
	return B;
}
static long[] copy(long A[]) {
	long B[]=new long[A.length];
	for(int i=0;i<A.length;i++) {
		B[i]=A[i];
	}
	return B;
}
static int[] input(int n) {
	int A[]=new int[n];
	   for(int i=0;i<n;i++) {
		   A[i]=sc.nextInt();
	   }
	   return A;
   }
static long[] inputL(int n) {
	long A[]=new long[n];
	   for(int i=0;i<n;i++) {
		   A[i]=sc.nextLong();
	   }
	   return A;
   }
static String[] inputS(int n) {
	String A[]=new String[n];
	   for(int i=0;i<n;i++) {
		   A[i]=sc.next();
	   }
	   return A;
   }
static long sum(int A[]) {
	long sum=0;
	for(int i : A) {
		sum+=i;
	}
	return sum;
}
static long sum(long A[]) {
	long sum=0;
	for(long i : A) {
		sum+=i;
	}
	return sum;
}
static void reverse(long A[]) {
	int n=A.length;
	long B[]=new long[n];
	for(int i=0;i<n;i++) {
		B[i]=A[n-i-1];
	}
	for(int i=0;i<n;i++)
		A[i]=B[i];
	
}
static void reverse(int A[]) {
	int n=A.length;
	int B[]=new int[n];
	for(int i=0;i<n;i++) {
		B[i]=A[n-i-1];
	}
	for(int i=0;i<n;i++)
		A[i]=B[i];
	
}
static void input(int A[],int B[]) {
	   for(int i=0;i<A.length;i++) {
		   A[i]=sc.nextInt();
		   B[i]=sc.nextInt();
	   }
}
static int[][] input(int n,int m){
	int A[][]=new int[n][m];
	for(int i=0;i<n;i++) {
		for(int j=0;j<m;j++) {
			A[i][j]=i();
		}
	}
	return A;
}
static char[][] charinput(int n,int m){
	char A[][]=new char[n][m];
	for(int i=0;i<n;i++) {
		String s=s();
		for(int j=0;j<m;j++) {
			A[i][j]=s.charAt(j);
		}
	}
	return A;
}
static int find(int A[],int a) {
	  if(A[a]==a)
		  return a;
	  return A[a]=find(A, A[a]);
}
static int max(int A[]) {
	int max=Integer.MIN_VALUE;
	for(int i=0;i<A.length;i++) {
		max=Math.max(max, A[i]);
	}
	return max;
}
static int min(int A[]) {
	int min=Integer.MAX_VALUE;
	for(int i=0;i<A.length;i++) {
		min=Math.min(min, A[i]);
	}
	return min;
}
static long max(long A[]) {
	long max=Long.MIN_VALUE;
	for(int i=0;i<A.length;i++) {
		max=Math.max(max, A[i]);
	}
	return max;
}
static long min(long A[]) {
	long min=Long.MAX_VALUE;
	for(int i=0;i<A.length;i++) {
		min=Math.min(min, A[i]);
	}
	return min;
}
static long [] prefix(long A[]) {
	long p[]=new long[A.length];
	p[0]=A[0];
	for(int i=1;i<A.length;i++)
		p[i]=p[i-1]+A[i];
	return p;
}
static long [] prefix(int A[]) {
	long p[]=new long[A.length];
	p[0]=A[0];
	for(int i=1;i<A.length;i++)
		p[i]=p[i-1]+A[i];
	return p;
}
static long [] suffix(long A[]) {
	long p[]=new long[A.length];
	p[A.length-1]=A[A.length-1];
	for(int i=A.length-2;i>=0;i--)
		p[i]=p[i+1]+A[i];
	return p;
}
static long [] suffix(int A[]) {
	long p[]=new long[A.length];
	p[A.length-1]=A[A.length-1];
	for(int i=A.length-2;i>=0;i--)
		p[i]=p[i+1]+A[i];
	return p;
}
static void fill(int dp[]) {
	Arrays.fill(dp, -1);
}
static void fill(int dp[][]) {
	for(int i=0;i<dp.length;i++)
	Arrays.fill(dp[i], -1);
}
static void fill(int dp[][][]) {
	for(int i=0;i<dp.length;i++) {
		for(int j=0;j<dp[0].length;j++) {
			Arrays.fill(dp[i][j],-1);
		}
	}
}
static void fill(int dp[][][][]) {
	for(int i=0;i<dp.length;i++) {
		for(int j=0;j<dp[0].length;j++) {
			for(int k=0;k<dp[0][0].length;k++) {
			Arrays.fill(dp[i][j][k],-1);
			}
		}
	}
}
static void fill(long dp[]) {
	Arrays.fill(dp, -1);
}
static void fill(long dp[][]) {
	for(int i=0;i<dp.length;i++)
	Arrays.fill(dp[i], -1);
}
static void fill(long dp[][][]) {
	for(int i=0;i<dp.length;i++) {
		for(int j=0;j<dp[0].length;j++) {
			Arrays.fill(dp[i][j],-1);
		}
	}
}
static void fill(long dp[][][][]) {
	for(int i=0;i<dp.length;i++) {
		for(int j=0;j<dp[0].length;j++) {
			for(int k=0;k<dp[0][0].length;k++) {
			Arrays.fill(dp[i][j][k],-1);
			}
		}
	}
}
static int min(int a,int b) {
	return Math.min(a, b);
}
static int min(int a,int b,int c) {
	return Math.min(a, Math.min(b, c));
}
static int min(int a,int b,int c,int d) {
	return Math.min(a, Math.min(b, Math.min(c, d)));
}
static int max(int a,int b) {
	return Math.max(a, b);
}
static int max(int a,int b,int c) {
	return Math.max(a, Math.max(b, c));
}
static int max(int a,int b,int c,int d) {
	return Math.max(a, Math.max(b, Math.max(c, d)));
}
static long min(long a,long b) {
	return Math.min(a, b);
}
static long min(long a,long b,long c) {
	return Math.min(a, Math.min(b, c));
}
static long min(long a,long b,long c,long d) {
	return Math.min(a, Math.min(b, Math.min(c, d)));
}
static long max(long a,long b) {
	return Math.max(a, b);
}
static long max(long a,long b,long c) {
	return Math.max(a, Math.max(b, c));
}
static long max(long a,long b,long c,long d) {
	return Math.max(a, Math.max(b, Math.max(c, d)));
}

static long power(long x, long y, long p)
{

	if(y==0)
		return 1;
	if(x==0)
		return 0;
    long res = 1;
    x = x % p;

    while (y > 0) {

        if (y % 2 == 1)
            res = (res * x) % p;

        y = y >> 1; 
        x = (x * x) % p;
    }

    return res;
}
static void print(int A[]) {
	for(int i : A) {
		System.out.print(i+" ");
	}
	System.out.println();
}
static void print(long A[]) {
	for(long i : A) {
		System.out.print(i+" ");
	}
	System.out.println();
}
static long mod(long x) {
	  return ((x%mod + mod)%mod);
}
static String reverse(String s) {
	StringBuffer p=new StringBuffer(s);
	p.reverse();
	return p.toString();
}

     static int i() {
    	 return sc.nextInt();
     }
     static String s() {
    	 return sc.next();
     }
     static long l() {
    	 return sc.nextLong();
     }  
     static void sort(int[] A){
        int n = A.length;
        Random rnd = new Random();
        for(int i=0; i<n; ++i){
            int tmp = A[i];
            int randomPos = i + rnd.nextInt(n-i);
            A[i] = A[randomPos];
            A[randomPos] = tmp;
        }
        Arrays.sort(A);
     }
     static void sort(long[] A){
	        int n = A.length;
	        Random rnd = new Random();
	        for(int i=0; i<n; ++i){
	            long tmp = A[i];
	            int randomPos = i + rnd.nextInt(n-i);
	            A[i] = A[randomPos];
	            A[randomPos] = tmp;
	        }
	        Arrays.sort(A);
	     }
  static String sort(String s) {
 	 Character ch[]=new Character[s.length()];
 	 for(int i=0;i<s.length();i++) {
 		 ch[i]=s.charAt(i);
 	 }
 	 Arrays.sort(ch);
 	 StringBuffer st=new StringBuffer("");
 	 for(int i=0;i<s.length();i++) {
 		 st.append(ch[i]);
 	 }
 	 return st.toString();
  }
  static HashMap<Integer,Integer> hash(int A[]){
	  HashMap<Integer,Integer> map=new HashMap<Integer, Integer>();
	  for(int i : A) {
		  if(map.containsKey(i)) {
			  map.put(i, map.get(i)+1);
		  }
		  else {
			  map.put(i, 1);
		  }
	  }
	  return map;
  }
  static TreeMap<Integer,Integer> tree(int A[]){
	  TreeMap<Integer,Integer> map=new TreeMap<Integer, Integer>();
	  for(int i : A) {
		  if(map.containsKey(i)) {
			  map.put(i, map.get(i)+1);
		  }
		  else {
			  map.put(i, 1);
		  }
	  }
	  return map;
  }
     static boolean prime(int n) 
	    { 
	        if (n <= 1) 
	            return false; 
	        if (n <= 3) 
	            return true; 
	        if (n % 2 == 0 || n % 3 == 0) 
	            return false; 
	        double sq=Math.sqrt(n);
	  
	        for (int i = 5; i <= sq; i = i + 6) 
	            if (n % i == 0 || n % (i + 2) == 0) 
	                return false; 
	        return true; 
	    } 
     static boolean prime(long n) 
	    { 
	        if (n <= 1) 
	            return false; 
	        if (n <= 3) 
	            return true; 
	        if (n % 2 == 0 || n % 3 == 0) 
	            return false; 
	        double sq=Math.sqrt(n);
	  
	        for (int i = 5; i <= sq; i = i + 6) 
	            if (n % i == 0 || n % (i + 2) == 0) 
	                return false; 
	        return true; 
	    } 
     static int gcd(int a, int b) 
     { 
         if (a == 0) 
             return b; 
         return gcd(b % a, a); 
     } 
     static long gcd(long a, long b) 
     { 
         if (a == 0) 
             return b; 
         return gcd(b % a, a); 
     } 
     
        
    static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            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; 
        } 
    } 
}