#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
#define rep(i, a, b) for(ll i = a; i < b; ++i)
#define rrep(i, a, b) for(ll i = a; i >= b; --i)
constexpr ll inf = 4e18;
struct SetupIO {
    SetupIO() {
        ios::sync_with_stdio(0);
        cin.tie(0);
        cout << fixed << setprecision(30);
    }
} setup_io;
using ull = unsigned long long;
int main(void) {
    int t;
    cin >> t;
    while(t--) {
        int n;
        ull x;
        cin >> n >> x;
        vector<int> c(n);
        rep(i, 0, n) {
            cin >> c[i];
        }
        if(bit_floor(x) >= (1ull << c[n - 1])) {
            int bit = -1;
            rrep(i, n - 1, 0) {
                if(!((1ull << c[i]) & x)) {
                    bit = c[i];
                    break;
                }
            }
            if(bit == -1) {
                cout << 0 << '\n';
                continue;
            }
            ull right = (x / (1ull << bit) * (1ull << bit)) | (1ull << bit);
            ull left = x / (1ull << bit) * (1ull << bit) - 1;
            cout << 2 * min(right - x, x - left) << '\n';
        } else {
            ull right = 1ull << c[n - 1];
            cout << 2 * (right - x) << '\n';
        }
    }
}