#include "bits/stdc++.h"
// #include "algotester.h"
// #include "algotester_generator.h"
using namespace std;

#define FOR(i,a,b) for (int i = (a); i < (b); i++)
#define RFOR(i,b,a) for (int i = (b) - 1; i >= (a); i--)
#define ITER(it,a) for (__typeof(a.begin()) it = a.begin(); it != a.end(); it++)
#define FILL(a,value) memset(a, value, sizeof(a))

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define PB push_back
#define MP make_pair

typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PII;

const double PI = acos(-1.0);
const int INF = 1000 * 1000 * 1000 + 7;
const LL LINF = INF * (LL) INF;

const int LEN = 31;

int get_zeros(int x)
{
	if (x == 0) return -1;
	int res = 0;
	while(x % 2 == 0)
	{
		x /= 2;
		res++;
	}
	return res;
}

void solve_test()
{
	int n, k;
	scanf("%d%d", &n, &k);
	VI a;
	FOR (i, 0, n)
	{
		int x;
		scanf("%d", &x);
		a.PB(x);
	}

	vector<VI> p(LEN);
	FOR (i, 0, n)
	{
		int x = get_zeros(a[i]);
		if (x != -1) p[x].PB(a[i]);
	}

	int s = 0;

	FOR (i, 0, n)
	{
		s ^= a[i];
	}

	int res = 0;

	FOR (it, 0, n)
	{
		int cur_res = s;

		s ^= a[it];
		s ^= a[it] + 1;

		FOR (i, 0, LEN)
		{
			if ((s & (1<<i)) == 0) continue;
			if ((SZ(p[i]) > 1) || ((SZ(p[i]) == 1) && p[i][0] != a[it]))
			{
				int cur = s ^ ((1<<(i+1)) - 1);
				cur_res = min(cur_res, cur);
			}
		}
		s ^= a[it];
		s ^= a[it] + 1;

		res = max(res, cur_res);
	}

	printf("%d\n", res);
}

int main(int argc, char* argv[])
{
	//ios::sync_with_stdio(false); cin.tie(0);

	int tt;
	scanf("%d", &tt);
	for (;tt;tt--)
	{
		solve_test();
	}

}