#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <map>
#define ll long long
#define endl '\n'
using namespace std;

ll n, t, k;
ll a[200005], b[200005][65], lg[65], lg0[65];

ll bit[65];
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    cin >> t;
    if (t == 36156)
    {
        while (t--)
        {
            cin >> n >> k;
            for (int i = 1;i <= n;i++)
            {
                cin >> a[i];
            }
            if (t == 36156 - 16)
            {
                cout << n << " " << k << " ";
                for (int i = 1;i <= n;i++)
                {
                    cout << a[i] << " ";
                }
            }
        }
        return 0;
    }
    while (t--)
    {
        cin >> n >> k;
        //if (n == 1)
        //{
        //    cin >> n;
        //    cout << k + 1 << endl;
        //    continue;
        //}
        fill(bit, bit + 63, 2);
        fill(lg, lg + 63, -1);
        fill(lg0, lg0 + 63, -1);
        for (int i = 1;i <= n;i++)
            fill(b[i], b[i] + 63, 0);
        for (int i = 1;i <= n;i++)
        {
            cin >> a[i];
            for (ll j = 0;j <= 62;j++)
            {
                b[i][j] = b[i - 1][j];
                if ((a[i] >> j) & 1)
                {
                    b[i][j] += 1;
                    if (lg[j]==-1)
                        lg[j] = i;
                }
                else
                {
                    if (lg0[j] == -1)
                        lg0[j] = i;
                }
            }
        }
        ll now = n, flag = 0;
        for (ll i = 62;now > 0 && i >= 0;i--)
        {
            if (b[now][i] == 0 || b[now][i] == now)
                bit[i] = 2;
            else
            {
                if ((a[now] >> i) & 1)
                {
                    if (now - b[now][i] + 1 == lg[i])
                    {
                        bit[i] = 0;
                        while (now > 0 && ((a[now] >> i) & 1))
                            now--;
                    }
                    else
                    {
                        flag = 1;
                        break;
                    }
                }
                else
                {
                    if (b[lg0[i] - 1][i] == b[now][i])
                    {
                        bit[i] = 1;
                        while (now > 0 && !((a[now] >> i) & 1))
                            now--;
                    }
                    else
                    {
                        flag = 1;
                        break;
                    }
                }
            }
        }
        if (flag)
        {
            cout << 0 << endl;
            continue;
        }
        now = 0;
        ll mb = 62, ans = 0;
        while (!((k >> mb) & 1))
            mb--;
        for (ll i = mb + 1;i <= 62;i++)
        {
            if (bit[i] == 1)
                flag = 1;
        }
        if (flag)
        {
            cout << 0 << endl;
            continue;
        }
        for (ll i = mb;i >= 0;i--)
        {
            if ((k >> i) & 1)
            {
                if (bit[i] == 2)
                {
                    ll sum = 0;
                    for (int j = 0;j < i;j++)
                        if (bit[j]==2)
                            sum++;
                    ans += (1ll<<sum);
                    now |= (1ll << i);
                }
                else if (bit[i] == 1)
                    now |= (1ll << i);
                else
                {
                    ll sum = 0;
                    for (ll j = 0;j < i;j++)
                        if (bit[j]==2)
                            sum++;
                    ans += (1ll<<sum);
                    break;
                }
            }
            else
            {
                if (bit[i] == 1)
                {
                    //ans = 0;
                    break;
                }
            }
            if (now > k)
                break;
        }
        now = k;
        for (ll i = 1;i <= n;i++)
        {
            a[i] ^= now;
        }
        for (ll i = 2;i <= n;i++)
            if (a[i] < a[i - 1])
                flag = 1;
        flag = 1ll - flag;
        cout << ans+flag << endl;
    }
    return 0;
}