ll d = 1 << 17;
	vector<vector<ll>> dec(d + 1,vector<ll>(18));
	for (ll i = 0; i <= d; i++) {
		for (ll msk = 0; msk < 18; msk++) {
			if (i & (1 << msk)) {
				dec[i][msk]++;
			}
			if(i>0)
			dec[i][msk] += dec[i - 1][msk];
		}
	}
	ll t;
	cin >> t;
	while (t--) {
		ll l, r;
		cin >> l >> r;
		vector<ll> a(r + 1);
		for (ll i = 0; i <= r; i++) {
			cin >> a[i];
		}
		ll cnt[18]={};
		for (ll i = 0; i <= r; i++) {
			for (ll msk = 0; msk < 18; msk++) {
				if (a[i] & (1 << msk)) {
					cnt[msk]++;
				}
			}
		}
		ll ans = 0;
		for (ll i = 0; i < 18; i++) {
			if (cnt[i] == r + 1 - dec[r][i]) {
				if ((r + 1) % 2 == 0 && dec[r][i] * 2 == r + 1)continue;
				ans += (1 << i);
			}
		}
		cout << ans << '\n';
	}