#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<unordered_set>
#include<utility>
#include<cassert>
#include<complex>
#include<numeric>
#include<array>
#include<chrono>
using namespace std;

//#define int long long
typedef long long ll;

typedef unsigned long long ul;
typedef unsigned int ui;
constexpr ll mod = 998244353;
//constexpr ll mod = 1000000007;
const ll INF = mod * mod;
typedef pair<int, int>P;

#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
#define all(v) (v).begin(),(v).end()
typedef pair<ll, ll> LP;

template<typename T>
void chmin(T& a, T b) {
	a = min(a, b);
}
template<typename T>
void chmax(T& a, T b) {
	a = max(a, b);
}
template<typename T>
void cinarray(vector<T>& v) {
	rep(i, v.size())cin >> v[i];
}
template<typename T>
void coutarray(vector<T>& v) {
	rep(i, v.size()) {
		if (i > 0)cout << " "; cout << v[i];
	}
	cout << "\n";
}
ll mod_pow(ll x, ll n, ll m = mod) {
	if (n < 0) {
		ll res = mod_pow(x, -n, m);
		return mod_pow(res, m - 2, m);
	}
	if (abs(x) >= m)x %= m;
	if (x < 0)x += m;
	//if (x == 0)return 0;
	ll res = 1;
	while (n) {
		if (n & 1)res = res * x % m;
		x = x * x % m; n >>= 1;
	}
	return res;
}
//mod should be <2^31
struct modint {
	int n;
	modint() :n(0) { ; }
	modint(ll m) {
		if (m < 0 || mod <= m) {
			m %= mod; if (m < 0)m += mod;
		}
		n = m;
	}
	operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
bool operator<(modint a, modint b) { return a.n < b.n; }
modint operator+=(modint& a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= (int)mod; return a; }
modint operator-=(modint& a, modint b) { a.n -= b.n; if (a.n < 0)a.n += (int)mod; return a; }
modint operator*=(modint& a, modint b) { a.n = ((ll)a.n * b.n) % mod; return a; }
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, ll n) {
	if (n == 0)return modint(1);
	modint res = (a * a) ^ (n / 2);
	if (n % 2)res = res * a;
	return res;
}

ll inv(ll a, ll p) {
	return (a == 1 ? 1 : (1 - p * inv(p % a, a)) / a + p);
}
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }
modint operator/=(modint& a, modint b) { a = a / b; return a; }
const int max_n = 1 << 21;
modint fact[max_n], factinv[max_n];
void init_f() {
	fact[0] = modint(1);
	for (int i = 0; i < max_n - 1; i++) {
		fact[i + 1] = fact[i] * modint(i + 1);
	}
	factinv[max_n - 1] = modint(1) / fact[max_n - 1];
	for (int i = max_n - 2; i >= 0; i--) {
		factinv[i] = factinv[i + 1] * modint(i + 1);
	}
}
modint comb(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[b] * factinv[a - b];
}
modint combP(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[a - b];
}

ll gcd(ll a, ll b) {
	a = abs(a); b = abs(b);
	if (a < b)swap(a, b);
	while (b) {
		ll r = a % b; a = b; b = r;
	}
	return a;
}
using ld = long double;
//typedef long double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-10;
const ld pi = acosl(-1.0);
template<typename T>
void addv(vector<T>& v, int loc, T val) {
	if (loc >= v.size())v.resize(loc + 1, 0);
	v[loc] += val;
}
/*const int mn = 2000005;
bool isp[mn];
vector<int> ps;
void init() {
	fill(isp + 2, isp + mn, true);
	for (int i = 2; i < mn; i++) {
		if (!isp[i])continue;
		ps.push_back(i);
		for (int j = 2 * i; j < mn; j += i) {
			isp[j] = false;
		}
	}
}*/

//[,val)
template<typename T>
auto prev_itr(set<T>& st, T val) {
	auto res = st.lower_bound(val);
	if (res == st.begin())return st.end();
	res--; return res;
}

//[val,)
template<typename T>
auto next_itr(set<T>& st, T val) {
	auto res = st.lower_bound(val);
	return res;
}
using mP = pair<modint, modint>;
mP operator+(mP a, mP b) {
	return { a.first + b.first,a.second + b.second };
}
mP operator+=(mP& a, mP b) {
	a = a + b; return a;
}
mP operator-(mP a, mP b) {
	return { a.first - b.first,a.second - b.second };
}
mP operator-=(mP& a, mP b) {
	a = a - b; return a;
}
LP operator+(LP a, LP b) {
	return { a.first + b.first,a.second + b.second };
}
LP operator+=(LP& a, LP b) {
	a = a + b; return a;
}
LP operator-(LP a, LP b) {
	return { a.first - b.first,a.second - b.second };
}
LP operator-=(LP& a, LP b) {
	a = a - b; return a;
}

mt19937 mt(time(0));

const string drul = "DRUL";
string senw = "SENW";
//DRUL,or SENW
int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };
//-----------------------------------------

void solve() {
	int n; ll y; cin >> n >> y;
	vector<ll> a(n);
	rep(i, n)cin >> a[i];
	vector<vector<LP>> vs(61);
	rep(j, 61) {
		ll k = (1ll << j);
		vector<LP> adv;
		adv.push_back({ 0,0 });
		adv.push_back({ k,0 });
		adv.push_back({ 2 * k,0 });
		rep(i, n) {
			ll r = a[i] % (2 * k);
			if (r & k) {
				adv.push_back({ 0,1 });
				adv.push_back({ 2 * k - r,-1 });
				adv.push_back({ 3 * k - r,1 });
				adv.push_back({ 2 * k,-1 });
			}
			else {
				adv.push_back({ k - r,1 });
				adv.push_back({ 2 * k - r,-1 });
			}
		}
		sort(all(adv));
		ll le = 0;
		int cur = 0;
		int b = 0; if (k & y)b = 1;
		rep(i, adv.size()) {
			ll x = adv[i].first;
			//[le,x)
			if (cur%2 == b && le < x) {
				vs[j].push_back({ le,x });
			}
			le = x;
			cur += adv[i].second;
		}
		/*cout << "hello " << j << "\n";
		for (auto p : vs[j]) {
			cout << p.first << " " << p.second << "\n";
		}*/
		//cout << "?? " << j << " " << vs[j].size() << "\n";
	}
	vector<pair<LP, ll>> v;
	v.push_back({ {0,1ll << 60},0 });
	per(j, 61) {
		auto& w = vs[j];
		vector<pair<LP, ll>> nv;
		int idv = 0;
		int idw = 0;
		while (idv < v.size() && idw < w.size()) {
			LP pl = v[idv].first;
			LP pr = w[idw];
			ll cl = max(pl.first, pr.first);
			ll cr = min(pl.second, pr.second);
			if (cl < cr) {
				//cout << "hi " << j << " " << cl << " " << cr << "\n";
				nv.push_back({ {cl,cr},v[idv].second });
			}
			if (pl.second < pr.second) {
				idv++;
			}
			else {
				idw++;
			}
		}
		ll k = (1ll << j);
		vector<pair<LP, ll>> nvl, nvr;
		//cout << "why " << j << "\n";
		for (auto p : nv) {
			//cout << p.first.first << " " << p.first.second << " " << p.second << "\n";
			if (p.first.first < k) {
				nvl.push_back(p);
			}
			else {
				auto pp = p;
				pp.first.first -= k;
				pp.first.second -= k;
				pp.second += k;
				nvr.push_back(pp);
			}
		}
		nv.clear();
		ll le = 0;
		int idl = 0, idr = 0;
		while (idl < nvl.size() && idr < nvr.size()) {
			auto pl = nvl[idl].first;
			auto pr = nvr[idr].first;
			ll cl, cr, val;
			if (pl.first < pr.first) {
				cl = pl.first, cr = pr.first, val = nvl[idl].second;
			}
			else {
				cl = pr.first, cr = pl.first, val = nvr[idr].second;
			}
			chmax(cl, le);
			if (cl < cr) {
				nv.push_back({ {cl,cr},val });
				le = cr;
			}
			cl = max(pl.first, pr.first);
			cr = min(pl.second, pr.second);
			val = min(nvl[idl].second, nvr[idr].second);
			assert(le <= cl);
			if (cl < cr) {
				nv.push_back({ {cl,cr},val });
				le = cr;
			}
			if (pl.second < pr.second) {
				cl = pl.first, cr = pl.second, val = nvl[idl].second;
			}
			else {
				cl = pr.first, cr = pr.second, val = nvr[idr].second;
			}
			chmax(cl, le);
			if (cl < cr) {
				nv.push_back({ {cl,cr},val });
				le = cr;
			}
			if (pl.second < pr.second) {
				idl++;
			}
			else {
				idr++;
			}
		}
		while (idl < nvl.size()) {
			auto pl = nvl[idl].first;
			ll cl = pl.first, cr = pl.second, val = nvl[idl].second;
			chmax(cl, le);
			if (cl < cr) {
				nv.push_back({ {cl,cr},val });
				le = cr;
			}
			idl++;
		}
		while (idr < nvr.size()) {
			auto pr = nvr[idr].first;
			ll cl = pr.first, cr = pr.second, val = nvr[idr].second;
			chmax(cl, le);
			if (cl < cr) {
				nv.push_back({ {cl,cr},val });
				le = cr;
			}
			idr++;
		}
		swap(v, nv);
		/*cout << j<<" hello "<<v.size() << "\n";
		for (auto p : v) {
			cout << p.first.first << " " << p.first.second << " "<<p.second<<"\n";
		}*/
	}
	ll ans = -1;
	if (v.size()) {
		assert(v.size() == 1);
		LP p0 = v[0].first;
		assert(v[0].first == LP({0, 1}));
		ans = v[0].second;
	}
	cout << ans << "\n";
}




signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout << fixed << setprecision(10);
	//init_f();
	//init();
	//expr();
	//while(true)
	int t; cin >> t; rep(i, t)
	solve();
	return 0;
}