#include <bits/stdc++.h>
using namespace std;

void fast_io() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
}

void solve() {
	int n;
	long long x;
	cin >> n >> x;
	vector<int> c;
	for (int i = 0; i < n; i++) {
		int a;
		cin >> a;
		if (x & (1LL << a)) {
			continue;
		}
		c.push_back(a);
	}
	if (c.empty()) {
		cout << 0 << endl;
		return;
	}
	for (int i = c.back() + 1; i <= 60; i++) {
		if (x & (1LL << i)) {
			x ^= (1LL << i);
		}
	}
	long long ans = (1LL << c.back());
	cout << 2 * (ans - x) << endl;
}
int main() {
	fast_io();
	int t;
	cin >> t;
	for (; t--;) {
		solve();
	}
}