#include "iostream"
#include "string"
#include "vector"
#include "algorithm"
using namespace std;

int main()
{	
	int t,n,i,j,k,q;
	int m=0;
	vector<string> vs;
	string s,base_string;
	string sub,sub_reverse;
	int max_sub_length=0;
	bool is_find;

	cin>>t;
	for(i=0;i<t;i++)
	{
		cin>>n;		
		for(j=0;j<n;j++)
		{	cin>>s;
			vs.push_back(s);
			if(j>0&&s.length()<vs[m].length())
				m=j;
		}
		base_string=vs[m];
		vs.erase(vs.begin()+m);
		
		for(j=0;j<base_string.length();j++)
		{
			for(k=1;k<=base_string.length()-j;k++)
			{
				sub=base_string.substr(j,k);
				sub_reverse=sub;
				reverse(sub_reverse.begin(),sub_reverse.end());				
				is_find=1;
				for(q=0;q<vs.size();q++)
				{
					if(vs[q].find(sub,0)==string::npos&&vs[q].find(sub_reverse,0)==string::npos)
					{	
						is_find=0;break;						
					}					
				}
				if(is_find&&sub.length()>max_sub_length)
					max_sub_length=sub.length();

				if(!is_find)
					break;


			}
		}
		cout<<max_sub_length<<endl;
		vs.clear();

	}
	


	return 0;
}