#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

void solve() {
  ll n, x;
  cin >> n >> x;
  vector<ll> c(n);
  rep(i, n) cin >> c[i];
  sort(c.begin(), c.end());
  for (ll i = n - 1; i >= 0; i--) {
    if (x & (1ll << c[i]))
      continue;
    ll y = x & ((1ll << c[i]) - 1);
    ll ans = (1ll << c[i]) - y;
    if (x > y) {
      ans = min(ans, y + 1);
    }
    ans *= 2;
    cout << ans << '\n';
    return;
  }
  cout << 0 << '\n';
}

int main() {
  std::cin.tie(nullptr);
  std::ios_base::sync_with_stdio(false);
  int T = 1;
  cin >> T;
  for (int t = 0; t < T; t++) {
    solve();
  }
  return 0;
}