#include <bits/stdc++.h>
 
using namespace std;
 
const int MaxN = 5e4 + 10;

struct Node {
	int to[2], cnt;
} nd[MaxN * 16];

int n, a[MaxN], pr[MaxN], ptr;
pair < int, int > t[2 * MaxN];
vector < pair < int, int > > q[MaxN];
long long cur, k;

pair < int, int > getPos(int l, int r) {
	l += n - 1;
	r += n - 1;
	pair < int, int > res = make_pair(MaxN, -1);
	while (l <= r) {
		if (l & 1) {
			res = min(res, t[l++]);
		}
		if (~r & 1) {
			res = min(res, t[r--]);
		}
		l >>= 1;
		r >>= 1;
	}
	return res;
}

void add(int l, int r, long long X, int S) {
	X = min(X, 65535LL);
	if (l > 0) {
		q[l - 1].push_back(make_pair(X + 100000, S));
	}
	q[r].push_back(make_pair(X, S));
}

void solve(int l, int r, long long x) {
	int p = getPos(l, r).second;
	if (p - l <= r - p) {
		for (int i = l; i <= p; ++i) {
			add(p, r, x / a[p], pr[i - 1]);
		}
	} else {
		for (int i = p; i <= r; ++i) {
			add(l - 1, p - 1, x / a[p], pr[i]);
		}
	}
	if (l < p) {
		solve(l, p - 1, x);
	}
	if (p < r) {
		solve(p + 1, r, x);
	}
}

void addNumber(int x) {
	int root = 0;
	nd[root].cnt += 1;
	for (int it = 15; it >= 0; --it) {
		int bit = (x >> it) & 1;
		if (nd[root].to[bit] == -1) {
			nd[root].to[bit] = ++ptr;
		}
		root = nd[root].to[bit];
		nd[root].cnt += 1;
	}
}

int takeL(int y, int x) {
	int res = 0;
	int root = 0, nw = 0;
	for (int it = 15; it >= 0; --it) {
		if (root == -1) {
			break;
		}
		int bit = (y >> it) & 1;
		if ((nw | (1 << it)) <= x) {
			int z = nd[root].to[bit];
			res += z != -1 ? nd[z].cnt : 0;
			root = nd[root].to[bit ^ 1];
			nw |= 1 << it;
		} else {
			root = nd[root].to[bit];
		}
	}
	if (nw <= x) {
		res += root != -1 ? nd[root].cnt : 0;
	}
	return res;
}

int main() {
	for (int i = 0; i < MaxN * 16; ++i) {
		nd[i].to[0] = nd[i].to[1] = -1;
	}
//	freopen("input.txt", "r", stdin);
	int tests = 1;
//	scanf("%d", &tests);
	while (tests --> 0) {
		scanf("%d%lld", &n, &k);
		assert (1 <= n && n <= 50000);
		assert (1 <= k && k <= 1LL * n * (n + 1) / 2);
		for (int i = 1; i <= n; ++i) {
			scanf("%d", &a[i]);
			assert (1 <= a[i] && a[i] <= 50000);
			pr[i] = a[i] ^ pr[i - 1];
			t[i + n - 1] = make_pair(a[i], i);
		}
		for (int i = n - 1; i > 0; --i) {
			t[i] = min(t[i + i], t[i + i + 1]);
		}
		long long l = 0, r = 50000 * 65535LL, res = -1;
		while (l <= r) {
			long long m = (l + r) / 2;
			cur = 0;
			solve(1, n, m);
			for (int i = 0; i <= n; ++i) {
				addNumber(pr[i]);
				for (auto it : q[i]) {
					int x = it.first % 100000, y = it.second;
					cur += (it.first >= 100000 ? -1 : +1) * takeL(y, x);
				}
			}
			for (int i = 0; i <= ptr; ++i) {
				nd[i].to[0] = nd[i].to[1] = -1;
				nd[i].cnt = 0;
			}
			for (int i = 0; i <= n; ++i) {
				q[i].clear();
			}
			ptr = 0;
			if (cur >= k) {
				res = m;
				r = m - 1;
			} else {
				l = m + 1;
			}
		}
		printf("%lld\n", res);
	}
	return 0;
}