#include <iostream>
#include <string>
#include <cstdio>
#include <cstdlib>
#include <set>
#include <map>
#include <vector>

using namespace std;
typedef long long LL;

vector<LL> t, t2;

int main() {
	int n, k;
	scanf("%d %d", &n, &k);
	t = vector<LL>(n+8);
	for (int i = 0; i < n; i++){
		scanf("%lld", &t[i]);
	}
	
	for (int i = 30; i >= 0; i--){
		LL msk = 1LL<<i;
		int db = 0;
		for (size_t i = 0; i < t.size(); i++){
			if (msk & t[i])
				db++;
		}
		if (db >= k) {
			t2 = vector<LL>(t.size());
			int db2 = 0;
			for (size_t i = 0; i < t.size(); i++){
				if (msk & t[i])
					t2[db2++] = t[i];
			}
			t = t2;
		}
		
	}
	
	LL ans = t[0];
	for (int i = 1; i < k; i++){
		ans &= t[i];
	}
	
	printf("%lld\n", ans);
	
	return 0;
}