#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for (int i = a; i < (b); i++)
#define Rep(i, a, b) for (int i = a; i >= (b); i--)
using ll = long long;

const int lgN = 20, N = 1e5 + 5;
int tot, cnt[N], c[N], son[2][N * lgN], val[N * lgN];
void clear() {
	rep(i, 0, tot + 1) {
		rep(b, 0, 2) son[b][i] = 0;
		val[i] = 0;
	}
	tot = 0;
}
void ins(int x, int d) {
	int u = 0;
	Rep(j, lgN - 1, 0) {
		const int b = x >> j & 1;
		if (!son[b][u]) son[b][u] = ++tot;
		val[u = son[b][u]] += d;
	}
}
int query(int x) {
	int u = 0, ret = x;
	Rep(j, lgN - 1, 0) {
		const int b = x >> j & 1;
		if (!b) {
			if (val[son[1][u]]) {
				ret |= 1 << j;
				u = son[1][u];
			} else u = son[0][u];
		} else {
			assert(ret >> j & 1);
			if (val[son[1][u]]) {
				ret |= (1 << j) - 1;
				break;
			} else u = son[0][u];
		}
	}
	return ret;
}
void solve() {
	clear();
	int n; cin >> n;
	rep(i, 1, n + 1) cin >> c[i];
	int ans = 0;
	rep(i, 1, n + 1) {
		if (cnt[c[i]]) ins(cnt[c[i]], -1);
		cnt[c[i]]++;
		ins(cnt[c[i]], 1);
		ans = max(ans, query(cnt[c[i]]));
	}
	cout << ans << endl;
	rep(i, 1, n + 1) cnt[c[i]] = 0;
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr), cout.tie(nullptr);
	int T = 1;
	cin >> T;
	while (T--) solve();
	return 0;
}