#include <set>

 #include <cstdio>

 #include <cstring>

 #include <algorithm>

 #include <queue>

 using namespace std;

 const int maxn = 1e5+;

 int Ma[maxn<<],Mp[maxn<<];

 set <int> pos;

 struct node{

     int mp,p;

     node(){}

     bool operator < (const node &rhs) const

     {

         if(mp == rhs.mp) return p > rhs.p;

         else return mp < rhs.mp;

     }

 };

 priority_queue<node> pq;

 void Manacher(int s[],int len)

 {

     int l = ;

     Ma[l++] = '$';

     Ma[l++] = '#';

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

     {

         Ma[l++] = s[i];

         Ma[l++] = '#';

     }

     Ma[l] = ;

     int mx = ,id = ;

     for(int i=;i<l;i++)

     {

         Mp[i] = mx > i? min(Mp[*id-i],mx-i) : ;

         while(Ma[i + Mp[i]] == Ma[i-Mp[i]]) Mp[i]++;

         if(Mp[i] + i > mx)

         {

             mx = Mp[i] + i;

             id = i;

         }

     }

 }

 int T,N;

 int save[maxn];

 int main()

 {

     scanf("%d",&T);

     int cas = ;

     while(T--)

     {

         scanf("%d",&N);

         for(int i=;i<N;i++) scanf("%d",&save[i]);

         Manacher(save,N);

         int ans = ;

         node tmp;

         while(!pq.empty()) pq.pop();

         pos.clear();

         for(int i=;i<*N+;i++)

         {

             if(Ma[i] == '#' && Mp[i] > )

             {

                 tmp.mp = Mp[i];

                 tmp.p = i;

                 pq.push(tmp);

             }

         }

         int cnt = ;

         //for(int i=0;i<2*N+1;i++) printf("%d\t",i); puts("");

         //for(int i=0;i<2*N+1;i++) printf("%c\t",Ma[i]=='#'?'#':Ma[i]+'0'); puts("");

         //for(int i=0;i<2*N+1;i++) printf("%d\t",Mp[i]); puts("");

         while(!pq.empty())

         {

             tmp = pq.top(); pq.pop();

             int cur = tmp.p,mp = tmp.mp;

             //printf("cur:%d mp:%d\n",cur,mp);

             int tmp_pos = ;

             if(cnt)

             {

                 auto it = pos.lower_bound(cur - (mp-) );

                 //printf("L:%d ",*it);

                 if(it != pos.end() && *it >= cur-(mp-)) ans = max(ans,cur-*it);

                 it = pos.lower_bound(cur + (mp-) ); it--;

                 //printf("R:%d\n",*it);

                 if(it != pos.end() && *it <= cur+(mp-)) ans = max(ans,*it-cur);

             }

             pos.insert(cur);

             cnt++;

         }

         printf("Case #%d: %d\n",++cas,ans/*);

     }

 }