#include<bits/stdc++.h>
const int N=55,p=998244353;
#define up(a,b,c)for(int a=b;a<=c;++a)
using namespace std;
int T,n,a[N];
struct mat{
	int a[N][N];
	mat(int x=0){
		up(i,0,n-1)fill(a[i],a[i]+n,0),a[i][i]=x;
	}
	mat operator*(mat b)const{
		mat c;
		up(i,0,n-1)up(j,0,n-1)up(k,0,n-1)
			c.a[i][j]=(c.a[i][j]+1ll*a[i][k]*b.a[k][j])%p;
		return c;
	}
	mat operator^(int m)const{
		mat A=*this,res(1);
		for(;m;A=A*A,m/=2)
			if(m&1)res=res*A;
		return res;
	}
};
mt19937 rnd;
int ls[N*N];
char ans[N];
vector<string>ccf;
struct gra{
	char to[N];
	int cc[N],p[N];
	mat A;
	gra()
	{
		A=mat();
		fill(cc,cc+n,0);
		int nd=0;
		map<char,int>noi;
		for(auto s:ccf)
		{
			for(char x:s)
				if(noi.find(x)==noi.end())
					to[nd]=x,noi[x]=nd,++nd;
			if(s.size()==1)++cc[noi[s[0]]];
			else ++A.a[noi[s[0]]][noi[s[1]]];
		}
		up(i,0,n-1)up(j,0,n-1)
			A.a[i][j]=ls[A.a[i][j]];
		A=A^100;
		iota(p,p+n,0);
		up(i,0,n-1)
			up(j,i+1,n-1)
				if(make_pair(cc[p[i]],A.a[p[i]][p[i]])<make_pair(cc[p[j]],A.a[p[j]][p[j]]))
					swap(p[i],p[j]);
	}
}O,P;
char dig(int x)
{
	if(x<26)return 'a'+x;
	return x-26+'A';
}
string dug(int x)
{
	if(x<n)return string("")+dig(x);
	else return dug(x/n)+dig(x%n);
}
int fig(char x)
{
	if(x>='a'&&x<='z')return x-'a';
	if(x>='A'&&x<='Z')return x-'A'+26;
}
int main(){
	cin>>T;
	while(T--){
		cin>>n;
		up(i,0,n*n)ls[i]=rnd()%p;
		ccf.clear();
		up(i,0,n-1)up(j,0,n-1)
			ccf.push_back(dug(i*j));
		O=gra();
		string s;
		ccf.clear();
		up(i,0,n-1)up(j,0,n-1)
			cin>>s,ccf.push_back(s);
		P=gra();
		up(i,0,n-1)
			ans[fig(O.to[O.p[i]])]=P.to[P.p[i]];
		up(i,0,n-1)
			cout<<ans[i];
		cout<<'\n';
	}
	return 0;
}