#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;
const int N=1000010;
int n,m,rank[N],sa[N],h[N],tmp[N],cnt[N],ans,a[N],s[N]; char str[N];
void suffixarray(int n,int m){int i,j,k;n++;for(i=0;i<2*n+5;i++)rank[i]=sa[i]=h[i]=tmp[i]=0;for(i=0;i<m;i++)cnt[i]=0;for(i=0;i<n;i++)cnt[rank[i]=s[i]]++;for(i=1;i<m;i++)cnt[i]+=cnt[i-1];for(i=0;i<n;i++)sa[--cnt[rank[i]]]=i;for(k=1;k<=n;k<<=1){for(i=0;i<n;i++){j=sa[i]-k;if(j<0)j+=n;tmp[cnt[rank[j]]++]=j;}sa[tmp[cnt[0]=0]]=j=0;for(i=1;i<n;i++){if(rank[tmp[i]]!=rank[tmp[i-1]]||rank[tmp[i]+k]!=rank[tmp[i-1]+k])cnt[++j]=i;sa[tmp[i]]=j;}memcpy(rank,sa,n*sizeof(int));memcpy(sa,tmp,n*sizeof(int));if(j>=n-1)break;}for(j=rank[h[i=k=0]=0];i<n-1;i++,k++)while(~k&&s[i]!=s[sa[j-1]+k])h[j]=k--,j=rank[sa[j]+1];
}int first=0,len[N],u,K;
vector<int> S[N];
int Min[15],Max[15];
bool check(int L){int cur=-1;for(int i=1;i<=u;i++){if(h[i]<L)S[++cur].clear();S[cur].push_back(i);}for(int i=0;i<=cur;i++){if(S[i].size()>=2*n){memset(Min,-1,sizeof(Min));memset(Max,-1,sizeof(Max));for(int j=0;j<S[i].size();j++){int k=S[i][j];int x=upper_bound(a,a+n+1,sa[k])-a-1;Min[x]=Min[x]==-1?sa[k]:min(Min[x],sa[k]);Max[x]=Max[x]==-1?sa[k]:max(Max[x],sa[k]);}bool flag=1;for(int i=0;i<n;i++){if(Min[i]==-1||Max[i]-Min[i]<L){flag=0;break;}}if(flag)return 1;}}return 0;
}int T;
int main(){scanf("%d",&T);while(T--){scanf("%d",&n);int tmp=200; u=0;for(int i=0;i<n;i++){scanf("%s",str);len[i]=strlen(str);for(int j=0;j<len[i];j++)s[u++]=(int)str[j];s[u++]=tmp++;}tmp=0; s[u]=0; //注意处理完的字符串最后封零for(int i=0;i<=n;i++){a[i]=tmp;if(i<n)tmp=tmp+(i==0?len[i]:len[i]+1);}suffixarray(u,310);int l=1,r=10000,ans=0;while(l<=r){int mid=(l+r)>>1;if(check(mid))ans=mid,l=mid+1;else r=mid-1;}printf("%d\n",ans);}return 0;
}