#include <bits/stdc++.h>
int calc(int a, int b) {
    int d = a | b, e = a & b;
    while(e & (e - 1))
        e &= e - 1;
    return d | std::max(e, e - 1);
}
int cnt[131072], a[131072], T, n;
int main() {
    std::cin >> T;
    while(T--) {
        std::cin >> n;
        for(int i = 1; i <= n; i++)
            cnt[i] = 0;
        for(int i = 1; i <= n; i++)
            std::cin >> a[i], cnt[a[i]]++;
        std::sort(cnt + 1, cnt + n + 1, std::greater<int>());
        int max = 0;
        for(int i = 2; i <= n; i++)
            max = std::max(max, calc(cnt[1], cnt[2]));
        std::cout << max << '\n';
    }
    return 0;
}