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.*;
import java.util.*;
import java.math.*;
import java.math.BigInteger;


public final class A
{    
	static PrintWriter out = new PrintWriter(System.out); 
	static StringBuilder ans=new StringBuilder();
	static FastReader in=new FastReader();
	static ArrayList<Integer> g[];
	static long mod=(long)1e9+7,INF=Long.MAX_VALUE;
	static boolean set[],col[]; 
	static int par[],tot[],partial[];
	static int D[],P[][];
	static long dp[][],max=0;
	//	static node1 seg[];
	//static pair moves[]= {new pair(-1,0),new pair(1,0), new pair(0,-1), new pair(0,1)};
	public static void main(String args[])throws IOException
	{				
		int T=i();
		outer:while(T-->0)
		{			
			int N=i(),M=i();
			char A[][]=new char[N][M];
			char B[][]=new char[N-1][M];
			//			ArrayList<Integer> index=new ArrayList<Integer>();
			for(int i=0; i<N; i++)
			{
				//				index.add(i);
				A[i]=in.next().toCharArray();
			}
			for(int i=0; i<N-1; i++)B[i]=in.next().toCharArray();
			int f[]=new int[26];
			int f2[]=new int[26];
			char last='*';
			for(int j=0; j<M; j++)
			{
				f2=new int[26];
				f=new int[26];
				for(int i=0; i<N; i++)
				{
					int x=A[i][j]-'a';
					f[x]++;
				}
				for(int i=0; i<N-1; i++)
				{
					int x=B[i][j]-'a';
					f2[x]++;
				}
				int index=-1;
				for(int i=0; i<26; i++)
				{
					if(f[i]>f2[i])
					{
						index=i;
						break;
					}
				}				
				last=(char)(index+'a');
				ans.append(last);							
			}
			ans.append("\n");			
		}
		System.out.println(ans);
		out.close();

	}

	//	static void build(int v,int tl,int tr,long A[])
	//	{
	//		if(tl==tr)
	//		{
	//			seg[v]=new node1(A[tl],A[tr],1,true);
	//			return ;
	//		}
	//		int tm=(tl+tr)/2;
	//		build(2*v,tl,tm,A);
	//		build(2*v+1,tm+1,tr,A);
	//		seg[v]=merge(seg[2*v],seg[2*v+1]);
	//	}
	//	static node1 ask(int v,int tl,int tr,int l,int r)
	//	{
	//		if(l>r)return new node1(0,0,0,false);//verify true or false
	//		if(tl==l && tr==r)return seg[v];
	//		int tm=(tl+tr)/2;
	//		node1 a=ask(v*2,tl,tm,l,Math.min(tm, r));
	//		node1 b=ask(v*2+1,tm+1,tr,Math.max(tm+1, l),r);
	//		return merge(a,b);
	//	}
	//	static node1 merge(node1 a,node1 b)
	//	{
	//		long s=0;
	//		long l1=a.L,r1=a.R,c1=a.cnt;
	//		long l2=b.L,r2=b.R,c2=b.cnt;
	//		long g=GCD(l2,r1); s=c1+c2;
	//		if(g==1)
	//		{
	//			s--;
	//			g=(l2*r1)/g;
	//			if(c1==1)
	//			{
	//				l1=g;
	//			}
	//			if(c2==1)r2=g;
	//			return new node1(l1,r2,s,true);
	//		}
	//		return new node1(l1,r2,s,a.leaf^b.leaf);
	//	}
	static long f(long l,long r,long a,long b,long N)
	{
		while(r-l>1)
		{
			long m=(l+r)/2;
			long x=m*b;
			if(N<x)
			{
				r=m;
				continue;
			}
			if((N-x)%a==0)r=m;
			else l=m;

		}
		return r;
	}
	static long f1(long a,long A[],long bits[],long sum)
	{
		long s=A.length;
		s=mul(s,a);
		s=(s+(sum%mod))%mod;
		long p=1L;
		for(long x:bits)
		{
			if((a&p)!=0)s=((s-mul(x,p))+mod)%mod;
			p<<=1;
		}
		return s;
	}
	static long f2(long a,long A[],long bits[])
	{
		long s=0;
		long p=1L;
		for(long x:bits)
		{
			if((a&p)!=0)
			{
				s=(s+mul(p,x))%mod;
			}
			p<<=1;
		}
		return s;
	}
	static long f(long x1,long y1,long x2,long y2)
	{
		return Math.abs(x1-x2)+Math.abs(y1-y2);
	}
	static long f(long x,long max,long s)
	{
		long l=-1,r=(x/s)+1;
		while(r-l>1)
		{
			long m=(l+r)/2;
			if(x-m*s>max)l=m;
			else r=m;
		}
		return l+1;
	}
	static int f(long A[],long x)
	{
		int l=-1,r=A.length;
		while(r-l>1)
		{
			int m=(l+r)/2;
			if(A[m]>=x)r=m;
			else l=m;			
		}
		return r;
	}



	static int bin(int x,ArrayList<Integer> A)
	{
		int l=0,r=A.size()-1;
		while(l<=r)
		{
			int m=(l+r)/2;
			int a=A.get(m);
			if(a==x)return m;
			if(a<x)l=m+1;
			else r=m-1;
		}
		return 0;
	}
	static int left(int x,ArrayList<Integer> A)
	{
		int l=-1,r=A.size();
		while(r-l>1)
		{
			int m=(l+r)/2;
			int a=A.get(m);
			if(a<=x)l=m;
			else r=m;
		}
		return l;
	}
	static int right(int x,ArrayList<Integer> A)
	{
		int l=-1,r=A.size();
		while(r-l>1)
		{
			int m=(l+r)/2;
			int a=A.get(m);
			if(a<x)l=m;
			else r=m;
		}
		return r;
	}



	static boolean equal(long A[],long B[])
	{
		for(int i=0; i<A.length; i++)if(A[i]!=B[i])return false;
		return true;	
	}


	static int max(int a ,int b,int c,int d)
	{
		a=Math.max(a, b);
		c=Math.max(c,d);
		return Math.max(a, c);
	}
	static int min(int a ,int b,int c,int d)
	{
		a=Math.min(a, b);
		c=Math.min(c,d);
		return Math.min(a, c);
	}



	static HashMap<Integer,Integer> Hash(int A[])
	{
		HashMap<Integer,Integer> mp=new HashMap<>();
		for(int a:A)
		{
			int f=mp.getOrDefault(a,0)+1;
			mp.put(a, f);
		}
		return mp;
	}
	static long mul(long a, long b)
	{
		return ( a %mod * 1L * b%mod )%mod;
	}
	static void swap(int A[],int a,int b)
	{
		int t=A[a];
		A[a]=A[b];
		A[b]=t;
	}


	static int find(int a)
	{
		if(par[a]<0)return a;
		return par[a]=find(par[a]);
	}
	static void union(int a,int b)
	{
		a=find(a);
		b=find(b);
		if(a!=b)
		{
			par[a]+=par[b];
			par[b]=a;
		}
	}
	static boolean isSorted(int A[])
	{
		for(int i=1; i<A.length; i++)
		{
			if(A[i]<A[i-1])return false;
		}
		return true;
	}

	static boolean isDivisible(StringBuilder X,int i,long num)
	{
		long r=0;
		for(; i<X.length(); i++)
		{
			r=r*10+(X.charAt(i)-'0');
			r=r%num;
		}
		return r==0;
	}    



	static int lower_Bound(int A[],int low,int high, int x) 
	{ 
		if (low > high) 
			if (x >= A[high]) 
				return A[high]; 

		int mid = (low + high) / 2; 

		if (A[mid] == x) 
			return A[mid]; 

		if (mid > 0 && A[mid - 1] <= x && x < A[mid]) 
			return A[mid - 1]; 

		if (x < A[mid]) 
			return lower_Bound( A, low, mid - 1, x); 

		return lower_Bound(A, mid + 1, high, x); 
	} 

	static String f(String A)
	{
		String X="";
		for(int i=A.length()-1; i>=0; i--)
		{
			int c=A.charAt(i)-'0';
			X+=(c+1)%2;
		}
		return X;
	}

	static void sort(long[] a) //check for long
	{
		ArrayList<Long> l=new ArrayList<>();
		for (long i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}

	static String swap(String X,int i,int j)
	{
		char ch[]=X.toCharArray();
		char a=ch[i];
		ch[i]=ch[j];
		ch[j]=a;
		return new String(ch);
	}

	static int sD(long n)  
	{  

		if (n % 2 == 0 )  
			return 2;  

		for (int i = 3; i * i <= n; i += 2) {  
			if (n % i == 0 )  
				return i;  
		}  

		return (int)n;  
	}  

	static void setGraph(int N)
	{
		tot=new int[N+1];
		partial=new int[N+1];
		D=new int[N+1];
		P=new int[N+1][(int)(Math.log(N)+10)];
		set=new boolean[N+1];
		g=new ArrayList[N+1];
		for(int i=0; i<=N; i++)
		{

			g[i]=new ArrayList<>();		
			D[i]=Integer.MAX_VALUE;
			//D2[i]=INF;
		}
	}



	static  long pow(long a,long b)
	{
		//long mod=1000000007;
		long pow=1;
		long x=a;
		while(b!=0)
		{
			if((b&1)!=0)pow=(pow*x)%mod;
			x=(x*x)%mod;
			b/=2;
		}
		return pow;
	}

	static long toggleBits(long x)//one's complement || Toggle bits
	{
		int n=(int)(Math.floor(Math.log(x)/Math.log(2)))+1;

		return ((1<<n)-1)^x;
	}

	static int countBits(long a)
	{
		return (int)(Math.log(a)/Math.log(2)+1);
	}

	static long fact(long N)
	{ 
		long n=2; 
		if(N<=1)return 1;
		else
		{
			for(int i=3; i<=N; i++)n=(n*i)%mod;
		}
		return n;
	}

	static int kadane(int A[])
	{
		int lsum=A[0],gsum=A[0];
		for(int i=1; i<A.length; i++)
		{
			lsum=Math.max(lsum+A[i],A[i]);
			gsum=Math.max(gsum,lsum);
		}
		return gsum;
	}

	static void sort(int[] a) {
		ArrayList<Integer> l=new ArrayList<>();
		for (int i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}

	static boolean isPrime(long N)
	{
		if (N<=1)  return false; 
		if (N<=3)  return true; 
		if (N%2 == 0 || N%3 == 0) return false; 
		for (int i=5; i*i<=N; i=i+6) 
			if (N%i == 0 || N%(i+2) == 0) 
				return false; 
		return true; 
	}
	static void print(char A[])
	{
		for(char c:A)System.out.print(c+" ");
		System.out.println();
	}
	static void print(boolean A[])
	{
		for(boolean c:A)System.out.print(c+" ");
		System.out.println();
	}
	static void print(int A[])
	{
		for(int a:A)System.out.print(a+" ");
		System.out.println();	
	}
	static void print(long A[])
	{
		for(long i:A)System.out.print(i+ " ");
		System.out.println();

	}
	static void print(ArrayList<Integer> A)
	{
		for(int a:A)System.out.print(a+" ");
		System.out.println();
	}

	static int i()
	{
		return in.nextInt();
	}

	static long l()
	{
		return in.nextLong();
	}

	static int[] input(int N){
		int A[]=new int[N];
		for(int i=0; i<N; i++)
		{
			A[i]=in.nextInt();
		}
		return A;
	}

	static long[] inputLong(int N)     {
		long A[]=new long[N];
		for(int i=0; i<A.length; i++)A[i]=in.nextLong();
		return A;
	}

	static long GCD(long a,long b) 
	{
		if(b==0)
		{
			return a;
		}
		else return GCD(b,a%b );
	}

}
//class node1
//{
//	long L,R,cnt;
//	boolean leaf;
//	node1(long l,long r,long c,boolean x)
//	{
//		this.leaf=x;
//		this.L=l;
//		this.R=r;
//		this.cnt=c;
//	}
//}


//Code For FastReader
//Code For FastReader
//Code For FastReader
//Code For FastReader
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;
	}

}