#include <bits/stdc++.h>
#define rep(i,a,b) for(int i=(a);i<(b);++i)
using namespace std;
using pii = pair<int,int>;
using ll = long long;
using ull = unsigned long long;
using lll = __int128;
using pll = pair<ll,ll>;
using vi = vector<int>;

#define fr first 
#define sc second

using ld = long double;

#define all(x) (x).begin(), (x).end()

const int maxn = 1e5+10, inf = 1e9+100;
const ll linf = 4e18+100;
const int mod = 998244353;

int a[maxn];
int psa[maxn][30];
vi inds[30],zinds[30];
int tot[30];


void solve () {
	int n;
	cin >> n;
	memset(tot,0,sizeof(tot));
	for(int i=0;i<30;i++)inds[i].clear(),zinds[i].clear();
	for(int i=0;i<30;i++)for(int j=0;j<=n;j++)psa[j][i]=0;
	for(int i=1;i<=n;i++)cin >> a[i];
	vi rel;
	for(int i=1;i<=n;i++){
		for(int j=0;j<30;j++){
			if((a[i]>>j)&1){
				tot[j]++;
				psa[i][j]++;
				inds[j].push_back(i);
			}
			else zinds[j].push_back(i);
		}
	}
	for(int i=1;i<=n;i++){
		for(int j=0;j<30;j++)psa[i][j]+=psa[i-1][j];
	}
	for(int j=0;j<30;j++){
		for(int i=2;i<=n;i++){
			if(psa[i][j]==i-1&&psa[i-1][j]==i-1){
				rel.push_back(i-1);
				if(i<n)rel.push_back(i);
			}
			if(psa[i][j]==i-2&&psa[i-1][j]==i-2){
				rel.push_back(i-1);
				if(i>2)rel.push_back(i-2);
			}
		}
		for(int i=n-1;i>=1;i--){
			if(tot[j]-psa[i-1][j]==n-i&&tot[j]-psa[i][j]==n-i){
				rel.push_back(i);
				if(i>1)rel.push_back(i-1);
			}
			if(tot[j]-psa[i-1][j]==n-i-1&&tot[j]-psa[i][j]==n-i-1){
				rel.push_back(i);
				if(i<n-1)rel.push_back(i+1);
			}
		}
	}
	sort(all(rel));
	rel.erase(unique(all(rel)),rel.end());
	if(rel.size()==0)rel.push_back(0);
	int ans = 0;
	for(int co : rel) {
		int tar = 0;
		vi cands;
		for(int j=29;j>=0;j--){
			if(tot[j]>=n-1)continue;
			if(psa[co][j]==co-1){
				tar=zinds[j][0];
				for(int i : inds[j]) if(i>co){
					cands.push_back(i);
				}
				break;
			}
			if(tot[j]-psa[co][j]==n-co-1){
				tar=zinds[j].back();
				for(int i : inds[j]) if(i<=co){
					cands.push_back(i);
				}
			}
		}
		cands.push_back(tar);
		for(int i : cands) {
			int cans = 0;
			for(int j=29;j>=0;j--){
				int rp = psa[co][j];
				if(tar!=i){
					rp += (tar<=co?-1:1)*(((a[tar]>>j)&1)-((a[i]>>j)&1));
				}
				if(rp==co)cans+=1<<j;
				if(tot[j]-rp==n-co)cans+=1<<j;
			}
			ans=max(ans,cans);
		}
	}
	cout << ans << "\n";
}



int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout<<fixed;
  cout.precision(20);
	int tc;
	cin >> tc;
	while(tc--)
  solve();
}