#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define ALL(v) v.begin(),v.end()
#define dbg(x) cerr << #x << ": " << (x) << endl;
template<class F, class S>
ostream& operator<<(ostream& os, pair<F,S>& p) {
    os << '(' << p.first << ',' << p.second << ')';
    return os;
}
template<class Iter>
void print(Iter beg, Iter end) {
    for (Iter itr = beg; itr != end; ++itr) {
        cerr << *itr << ' ';
    }
    cerr << '\n';
}
inline bool naraba(bool a, bool b) { return (!a || b); }

ll solve() {
    int N;
    ll X;
    cin >> N >> X;
    vector<int> C(N);
    for (int i = 0; i < N; ++i) cin >> C[i];

    ll ans = 0;
    for (int i = 0; i < N; ++i) {
        if (X >> C[i] & 1) continue;

        ll W = 1LL << C[i]+1;
        ll L = X / W * W - 1;
        ll R = L + 1 + (1LL << C[i]);
        // dbg(W)
        // dbg(L)
        // dbg(R)
        if (L < 0) {
            // dbg(R-X)
            ans = max(ans, R-X);
        } else {
            // dbg(min(X-L, R-X))
            ans = max(ans, min(X-L, R-X));
        }
    }
    return ans << 1;
}

int main() {
    int T;
    cin >> T;
    while (T--) {
        cout << solve() << '\n';
    }
}