#include <bits/stdc++.h>
using namespace std;
#define all(v) (v).begin(),(v).end()
#define pb(a) push_back(a)
#define rep(i, n) for(int i=0;i<n;i++)
#define foa(e, v) for(auto& e : v)
using ll = long long;
const ll MOD7 = 1000000007, MOD998 = 998244353, INF = (1LL << 60);
#define dout(a) cout<<fixed<<setprecision(10)<<a<<endl;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    ll t;
    cin >> t;
    rep(_, t) {

        ll n, x;
        cin >> n >> x;
        ll Ma = -1;
        rep(i, n) {
            ll a; cin >> a;
            if(x >> a & 1LL) continue;
            // else st.insert(a);
            Ma = max(Ma, a);
        }
        if(Ma == -1) {
            cout << 0 << endl;
            continue;
        }
        ll ans = INF;
        if(x >= (1LL << (Ma + 1))) {
            ll val = (x & ((1LL << Ma) - 1));
            ans = min(ans, val + 1);
        }
        x &= ((1LL << Ma) - 1);
        ans = min(ans, (1LL << Ma) - x);
        cout << ans * 2 << endl;
    }        
    return 0;
}