#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int Mod=1e9+7;
const ll INF = 10000000000000;
const int N = 1e6+7;
 
    void solve() {
       int n,l;
       cin >> n >> l;
       vector<vector<int>> a(l,vector<int>(2,0));
       for(int i=0;i<n;i++){
        int x;cin >> x;
        for(int j=0;j<l;j++){
            int bit =(x>>j)&1;
            a[j][bit]+=1;
        }
       }
       ll y=0;
       for(int i=0;i<l;i++){
           if(a[i][1]>a[i][0]) y+=1<<i; 
       }
       cout << y << '\n';
    }
int main(){ 
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
 
    int t;
    cin >> t;
    while (t--) solve();
 
    return 0;
}

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7
3 5
18 9 21
3 5
18 18 18
1 1
1
5 30
1 2 3 4 5
6 10
99 35 85 46 78 55
2 1
0 1
8 8
5 16 42 15 83 65 78 42