#include <bits/stdc++.h>
using namespace std;
using ll = long long;
 
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
 
    int T; cin >> T;
    while(T--){
        int n,q; cin>>n>>q;
        vector<ll>a(n);
        for(int i=0;i<n;i++) cin>>a[i];
 
        ll xa = 0;
        for(ll x: a) xa ^= x;
 
        while(q--){
            ll c; cin >> c;
            ll need = xa ^ c;
            if(need == 0){
                cout << 0 << "\n";
                continue;
            }
            ll best = LLONG_MAX;
            for(ll x: a){
                ll t = x ^ need;
                if(t >= x) best = min(best, t - x);
            }
            if(best == LLONG_MAX) cout << -1 << "\n";
            else cout << best << "\n";
        }
    }
}
 

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4
2 1
5 7
9
3 1
9 9 8
24
6 4
1 1 4 5 1 4
10
20
30
40
1 1
0
0