#include<bits/stdc++.h>
using namespace std;
#define min(a,b) ((a)<(b)?(a):(b))
const int maxn=1e6;
int a[maxn],p[maxn];
void Manacher(int n){
    a[0]=-2;a[n+1]=-1;a[n+2]=-3;
    int mx=0,id=0;
    for(int i=1;i<=n+1;i++){    //需要处理到n+1
        if(i<mx){
            p[i]=min(p[id*2-i],mx-i);   //这里写的时候写成mx-id，SB了。
        }else{
            p[i]=1;
        }
        for(;a[i+p[i]]==a[i-p[i]];++p[i]);  //-2，-3防越界
        if(i+p[i]>mx){
            mx=p[i]+i;
            id=i;
        }
    }
    for(int i=1;i<=n+1;++i){
        --p[i];
    } 
}
int main(){
 //   freopen("1003.in","r",stdin);
//    freopen("OUTTTT.txt","w",stdout);
    int t,n,cnt=0;
    scanf("%d",&t);
    while(t--){
        scanf("%d",&n);
        for(int i=1;i<=2*n;i+=2){
            a[i]=-1;
            scanf("%d",&a[i+1]);
        }

        Manacher(2*n);
        int maxv=0,j;
        for(int i=1;i<=2*n;i+=2){           //2*n
            for(j=i+p[i];j-maxv>i;j-=2){ //逆序枚举。manacher算法保证j<=2*n+1 
                if(j-p[j]<=i){
                    maxv=j-i;
                    break;
                }
            }
        }
        maxv=3*(maxv/2);
        printf("Case #%d: %d\n",++cnt,maxv);
    }
    return 0;
}