#include<cstdio>

 #include<iostream>

 #include<cmath>

 #include<cstring>

 #include<algorithm>

 int len,num[],ws[],wv[],wa[],wb[],h[],sa[],rank[];

 int f[][],N,b[];

 char s[];

 int read(){

     int t=,f=;char ch=getchar();

     while (ch<''||ch>''){if (ch=='-')f=-;ch=getchar();}

     while (''<=ch&&ch<=''){t=t*+ch-'';ch=getchar();}

     return t*f;

 }

 bool cmp(int *r,int a,int b,int l){

     return r[a]==r[b]&&r[a+l]==r[b+l];

 }

 void da(int *r,int *sa,int n,int m){

     int *t,*x=wa,*y=wb,i,j,k,p;

     for (i=;i<m;i++) ws[i]=;

     for (i=;i<n;i++) x[i]=r[i];

     for (i=;i<n;i++) ws[x[i]]++;

     for (i=;i<m;i++) ws[i]+=ws[i-];

     for (i=n-;i>=;i--) sa[--ws[x[i]]]=i;

     for (j=,p=;p<n;j*=,m=p){

         for (p=,i=n-j;i<n;i++) y[p++]=i;

         for (i=;i<n;i++) if (sa[i]>=j) y[p++]=sa[i]-j;

         for (i=;i<m;i++) ws[i]=;

         for (i=;i<n;i++) wv[i]=x[y[i]];

         for (i=;i<n;i++) ws[wv[i]]++;

         for (i=;i<m;i++) ws[i]+=ws[i-];

         for (i=n-;i>=;i--) sa[--ws[wv[i]]]=y[i];

         for (t=x,x=y,y=t,i=,x[sa[]]=,p=;i<n;i++){

             x[sa[i]]=cmp(y,sa[i-],sa[i],j)?p-:p++;

         }

     }

 }

 void cal(int *r,int n){

     int i,j,k=;

     for (int i=;i<=n;i++) rank[sa[i]]=i;

     for (int i=;i<n;h[rank[i++]]=k){

         for (k?k--:,j=sa[rank[i]-];r[j+k]==r[i+k];k++);

     }

 }

 bool check(int mid){

     int l,r;

     for (int i=;i<=len;i++){

         l=i;

         while (l<=len&&h[l]<mid) l++;

         r=l;

         while (r<=len&&h[r]>=mid) r++;

         for (int j=;j<=N;j++) f[j][]=0x3f3f3f3f,f[j][]=-0x3f3f3f3f;

         for (int j=l-;j<=r-;j++){

             int k=b[sa[j]];

             if (k==N+) continue;

             f[k][]=std::min(f[k][],sa[j]);

             f[k][]=std::max(f[k][],sa[j]);

         }

         int j=;

         for (j=;j<=N;j++){

             if (f[j][]==0x3f3f3f3f) break;

             if (f[j][]-f[j][]<mid) break;

         }

         if (j>N) return ;

         i=r;

     }

     return ;

 }

 void solve(){

     int l=,r=,ans=;

     while (l<=r){

         int mid=(l+r)>>;

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

         else r=mid-;

     }

     printf("%d ",ans);

 }

 int main(){

     int T=read();

     while (T--){

         len=;

         int n=read();

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

             scanf("%s",s+);

             int Len=strlen(s+);

             for (int j=;j<=Len;j++)

              num[len]=s[j],b[len++]=i;

             if (i<n) num[len]=+i,b[len++]=n+;

         }

         num[len]=;b[len]=n+;

         da(num,sa,len+,);

         cal(num,len);

         N=n;

         solve();

     }

 }