#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<iostream>
#include<math.h>
#include<vector>
using namespace std;
#define mem(a,t) memset(a,t,sizeof(a))
#define N 100005
const int inf=0x1f1f1f1f;
const double eps=1e-7;
const int M=10000;
bool cmp(int a,int b)
{
    return a>b;
}
int a[N],n;

int gcd(int a,int b)
{
    int r=a%b;
    while(r)
    {
        a=b;
        b=r;
        r=a%b;
    }
    return b;
}
int findd(int x)
{
    int l,r,m;
    l=0;
    r=n-1;
    while(l<=r)
    {
        m=(l+r)>>1;
        if(a[m]==x)
            return 1;
        else if(a[m]<x)
            l=m+1;
        else
            r=m-1;
    }
    return 0;
}
int work(int n)
{
    int i,cnt,t;
    int l,r;
    for(i=a[n-1]; i>=2; i--)
    {
        t=i;
        cnt=0;
        while(t<=a[n-1])
        {
            l=lower_bound(a,a+n,t)-a;
            r=upper_bound(a,a+n,t)-a;
            t+=i;
            //printf("%d %d %d\n",i,l,r);
            if(r>=l+2)
                cnt=2;
            else if(r>=l+1)
                cnt++;
            if(cnt>=2)
                break;
        }
        if(cnt>=2)
            break;
    }
    return i;
}
int main()
{
    int i,j,T,t,cnt=1;

    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&n);
        for(i=j=0; i<n; i++)
        {

            scanf("%d",&a[i]);
        }
        sort(a,a+n);

        int ans=work(n);
        printf("Case #%d: %d\n",cnt++,ans);
    }
    return 0;
}