#include <cstdio>
#include <algorithm>
#include <cstring>
#include <iostream>
#include <string>
#include <vector>
#define FOR(i, n, m) for(int i = n; i <= m; i++)
#define REP(i, n, m) for(int i = n; i >= m; i--)
using  namespace std;
typedef long long ll;
const int maxn = 100010;
int cnt[maxn];
int main()
{
    int t, cas = 1;
    scanf("%d", &t);
    while(t--)
    {
        memset(cnt, 0, sizeof(cnt));
        int n, x, M = 1;
        scanf("%d", &n);
        FOR(i, 0, n-1) scanf("%d", &x), cnt[x]++, M = max(M, x);
        int ans = 1;
        for(int i = M; i >= 2; i--) {
            int C = 0;
            for(int j = i; j <= M; j += i) if(cnt[j]) C+=cnt[j];
            if(C >= 2) {
                ans = i;
                break;
            }
        }
        printf("Case #%d: %d\n", cas++, ans);
    }
    // system("pause");
    return 0;
}