#include<bits/stdc++.h>

using namespace std;
using LL = long long;
using ll = long long;
const int N = 200005;
#define rep(i,a ,b )  for(int i = a ;i<=b;i++)
#define pre(i,a ,b )  for(int i = a ;i>=b;i--)
#define pb push_back
#define sc(x) scanf("%d",&x)

const int mod=1e9+9;
int hz[35];
int get(int x,int y){
	int res=0;
	pre(i,20,0){
		int u=0,v=0;
		if((x&(1<<i))){
			u=1;
		}
		if((y&(1<<i))){
			v=1;
		}
		if(!u&&!v)continue;
		//cout<<i<<" "<<u<<" "<<v<<endl;
		if(u==v){
			res|=hz[i];
			return res;
		}
		else{
			res|=(1<<i);
		}
	}
	return res;
}
int cnt[N];
void solve() {
	int n;
	sc(n);
	rep(i,1,n)cnt[i]=0;vector<int>p[25];
	rep(i,1,n){
		int x;sc(x);cnt[x]++;
	}
	int mx=0,cmx=0;
	rep(i,1,n){
		int nw=0;if(!cnt[i])continue;
		int x=cnt[i];
		if(mx<cnt[i])mx=cnt[i];
		else if(cmx<cnt[i])cmx=cnt[i];
	}
	if(!cmx){
		printf("%d\n",mx);
	}
	else
	printf("%d\n",get(mx,cmx));

}


int main() {

    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    hz[0]=1;
	rep(i,1,20){
		hz[i]=(hz[i-1]|(1<<i));
	}
    int t = 1;
    cin >> t ;

    while (t--) {
        solve();
    }

    return 0;


}