#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using lld = double;
#define srt(a) sort(a.begin(),a.end());
#define rsrt(a) sort(a.rbegin(),a.rend());
#define pb push_back
using pll=pair<ll,ll>;
#define fi(a,b,c) for(ll a=b;a<c;a++)
#define f(a,c) for(ll a=0;a<c;a++)
#define rf(a,c) for(ll a=c;a>=0;a--)
#define cye cout<<"Yes\n"
#define cno cout<<"No\n"
#define vll vector<ll> 
ll mod=676767677,N=1e6;
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    ll t;
    cin>>t;
    while(t--){
    ll n,ans=0;
    cin>>n;
    vll a(n);
    f(i,n)cin>>a[i];
    f(i,n){
        fi(j,i+1,n){
            ans=max(ans,a[i]^a[j]);
        }
    }
    cout<<ans<<'\n';
    }
    return 0;
}

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MwoyCjY3IDY3CjMKMSAyIDMKMTAKNjcgNjY3IDE2NyA4NjcgMjY3IDQ2NyAzNjcgNTY3IDc2NyA5NjcK

3
2
67 67
3
1 2 3
10
67 667 167 867 267 467 367 567 767 967