#include<stdio.h>
#include<string.h>

int t,n;
char str[100][101];

int searchMaxSubString(char *source){
	int subStrLen=strlen(source),sourceStrLen=strlen(source);
	int i,j;
	bool foundMaxSubstr;
	char subStr[101],revSubStr[101];

	while(subStrLen>0){  //搜索不同长度的子串，从最长的子串开始搜索
		for(i=0;i<=sourceStrLen-subStrLen;i++){
			//搜素长度为subStrlen的全部子串
			strncpy(subStr,source+i,subStrLen);
			strncpy(revSubStr,source+i,subStrLen);
			subStr[subStrLen]=revSubStr[subStrLen]='\0';
			strrev(revSubStr);
			foundMaxSubstr=true;
			for(j=0;j<n;j++)
				if(strstr(str[j],subStr)==NULL&&strstr(str[j],revSubStr)==NULL){
					foundMaxSubstr=false;
					break;
				}
				if(foundMaxSubstr)
					return(subStrLen);
		}
		subStrLen--;
	}

	return(0);
}

void main()
{
	int i,minStrLen,subStrLen;
	char minStr[101];

	scanf("%d",&t);
	while(t--){
		scanf("%d",&n);
		minStrLen=100;
		for(i=0;i<n;i++){	//输入一组字符串
			scanf("%s",str[i]);
			if(strlen(str[i])<minStrLen){	//寻找输入字符串中的最短字符
				strcpy(minStr,str[i]);
				minStrLen=strlen(minStr);
			}
		}
		subStrLen=searchMaxSubString(minStr);//搜索满足条件的最长字符串
		printf("%d\n",subStrLen);
	}
}