#include<bits/stdc++.h>
#define int long long
#define ull unsigned long long
using namespace std;
typedef pair<int,int>PII;
typedef pair<int,PII>PPI;
typedef array<int,3>ar;
typedef __int128 i28; 
const int N=1e6+7;
const int N1=1e9+9;
const int M=998244353;
const ull mask = std::chrono::steady_clock::now().time_since_epoch().count();
mt19937_64 rng(time(0));
const int M1=19260817;
const int base=233;
const int base1=131;
const int INF = 0x3f3f3f3f;
int a[N];
int cnt[N];
void solve()
{
	int n;
	cin>>n;
	
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
		cnt[a[i]]++;
	}
	int x=0,y=0;
	for(int i=1;i<=n;i++)
	{
		if(cnt[i]>x)
		{
			y=x;
			x=cnt[i];
		}
		else if(cnt[i]>y) y=cnt[i];
	}
	int ans=0;
	for(int i=1;i<=x;i++)
	{
		int now=0,an=0;
		for(int j=30;j>=0;j--)
		{
			int x=(i>>j)&1;
			if(x==0)
			{
				if(now+(1<<j)<=y)
				{
					now+=1<<j;
					an+=1<<j;
				}
			}
			else 
			{
				an+=1<<j;
			}
		}
		ans=max(ans,an);
	}
	cout<<ans<<"\n";
}	
signed main()
{
	std::ios::sync_with_stdio(false);
	cout.tie(0);cin.tie(0);
	int _=1;
	cin>>_;
	while(_--)
	{
		solve();
	}
}