/* -*- coding: utf-8 -*-
 *
 * 2844.cc:  No.2844 Birthday Party Decoration - yukicoder
 */

#include<cstdio>
#include<algorithm>
#include<utility>

using namespace std;

/* constant */

const int MAX_N = 60;
const int BN = 60;
const long long LINF = 1LL << (BN + 1);

/* typedef */

using ll = long long;
using pll = pair<ll,ll>;

/* global variables */

int cs[MAX_N];
pll ps[MAX_N + 1];

/* subroutines */

/* main */

int main() {
  int tn;
  scanf("%d", &tn);

  while (tn--) {
    int n;
    ll x;
    scanf("%d%lld", &n, &x);
    for (int i = 0; i < n; i++) scanf("%d", cs + i);

    ll r = x;
    int m = 0;
    for (int i = 0; i < n; i++) {
      ll bi = (1LL << cs[i]);
      if ((x & bi) == 0) {
	ll li = (x & ~(bi - 1)) - 1;
	ll ri = (x & ~(bi - 1)) | bi;
	if (li < 0) r = max(r, ri);
	else ps[m++] = {li, ri};
      }
    }

    ll mind = LINF;
    if (m > 0) {
      sort(ps, ps + m);
      ps[m] = {x, x};
      ll l = ps[0].first;
      mind = r - l;

      for (int i = 0; i < m; i++) {
	r = max(r, ps[i].second);
	l = ps[i + 1].first;
	mind = min(mind, r - l);
      }
    }
    else
      mind = r - x;

    printf("%lld\n", mind * 2);
  }

  return 0;
}