#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int INF = 1e9 + 10;
const ll INFL = 4e18;

int main() {
    int T;
    cin >> T;

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

        ll ans = INFL;
        {
            ll lo = X - 1, hi = INFL;
            while (hi - lo > 1) {
                ll mid = (hi + lo) / 2;

                int dif = -1;
                for (int i = 60; i >= 0; i--) {
                    if ((mid >> i & 1) != (X >> i & 1)) {
                        dif = i;
                        break;
                    }
                }

                vector<int> need;
                for (int i = 0; i < N; i++) {
                    if (!(X >> C[i] & 1)) {
                        need.push_back(C[i]);
                    }
                }

                if (!need.empty() && need.back() > dif) {
                    lo = mid;
                } else {
                    hi = mid;
                }
            }
            ans = min(ans, 2ll * abs(X - hi));
        }

        {
            ll lo = -1, hi = X + 1;
            while (hi - lo > 1) {
                ll mid = (hi + lo) / 2;

                int dif = 61;
                for (int i = 60; i >= 0; i--) {
                    if ((mid >> i) != (X >> i)) {
                        dif = i;
                        break;
                    }
                }

                vector<int> need;
                for (int i = 0; i < N; i++) {
                    if (!(X >> C[i])) {
                        need.push_back(C[i]);
                    }
                }

                if (!need.empty() && need.back() > dif) {
                    hi = mid;
                } else {
                    lo = mid;
                }
            }
            if (lo > 0 && hi < X) {
                ans = min(ans, 2ll * abs(X - lo));
            }
        }

        cout << ans << endl;
    }
}