B

#include <bits/stdc++.h>

using namespace std;

#define _test   int _TEST; cin>>_TEST; while(_TEST--)

int main()
{
    _test
    {
        int n;
        cin>>n;

        vector<int> a(n);
        for(auto &e: a)     cin>>e;

        int ans = 0;
        for(auto e: a)      ans ^= e;

        int tmp = ans;

        for(auto e: a)
            ans = min(ans, (e^tmp));

        cout<<ans<<"\n";
    }
}