#include <cstdio>

#include <cstring>

#include <vector>

#include <algorithm>

using namespace std;

const int N=200010;

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 len[N],u,K;

vector<int> S[N];

bool vis[N];

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()>=n){

            memset(vis,0,sizeof(vis));

            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;

                vis[x]=1;

            }int count=0;

            for(int j=0;j<n;j++)if(vis[j])count++;

            if(count>=n)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++;

            for(int j=len[i]-1;j>=0;j--)s[u++]=(int)str[j];

            s[u++]=tmp++;

        }tmp=0; s[u]=0;

        for(int i=0;i<=n;i++){

            a[i]=tmp;

            if(i<n)tmp=tmp+(i==0?2*len[i]+1:2*len[i]+2);

        }suffixarray(u,410);

        int l=1,r=100,ans=0;

        while(l<=r){

            int mid=(l+r)>>1;

            if(check(mid))ans=mid,l=mid+1;

            else r=mid-1;

        }if(n==1)printf("%d\n",len[0]);

		else printf("%d\n",ans);

    }return 0;

}