#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
istream &operator>>(istream &is, modint &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint &a) { return os << a.val(); }
istream &operator>>(istream &is, modint998244353 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint998244353 &a) { return os << a.val(); }
istream &operator>>(istream &is, modint1000000007 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint1000000007 &a) { return os << a.val(); } 

typedef long long ll;
typedef vector<vector<int>> Graph;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define FOR(i,l,r) for (int i = l;i < (int)(r); i++)
#define rep(i,n) for (int i = 0;i < (int)(n); i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define my_sort(x) sort(x.begin(), x.end())
#define my_max(x) *max_element(all(x))
#define my_min(x) *min_element(all(x))
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int INF = (1<<30) - 1;
const ll LINF = (1LL<<62) - 1;
const int MOD = 998244353;
const int MOD2 = 1e9+7;
const double PI = acos(-1);
vector<int> di = {1,0,-1,0};
vector<int> dj = {0,1,0,-1};

#ifdef LOCAL
#  include <debug_print.hpp>
#  define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define debug(...) (static_cast<void>(0))
#endif

void solve(){
    ll N, X; cin >> N >> X;
    const int L = 60;
    vector<ll> a(L), b(L);

    ll Y = 0;
    rep(_, N){
        int c; cin >> c;
        a[c] = 1;
        Y = (1LL << c);
    }
    rep(bit,L)if((X&(1LL<<bit))) b[bit] = 1;

    if(Y > X){
        cout << 2LL * (Y - X) << endl;
        return;
    }


    debug(a, b);
    // 最上位bit
    bool f = false;
    for(ll h = L - 1; h >= 0; h--){
        if(a[h] == 1 && b[h] == 0){
            ll V = 0;
            for(ll i = 0; i < h; i++){
                V += b[i] * (1LL << i);
            }
            cout << 2LL * min(V + 1LL, (1LL<<h) - V) << endl;
            return;
        }
    }

    cout << 0 << endl;
}

int main(){
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    int t; cin >>t;
    while(t--) solve();
}