#include<iostream>
#include <vector>
#include <utility>

using namespace std;

int main(){
	int n, k;
	cin >> n >> k;
	vector<int> v(n);
	vector <vector<int>> can(n, vector<int>(31));
	int j = 0;
	for(int& x : v){
		cin >> x;
		for(int i = 30; i >= 0; i--){
			if(x >= (1 << i)){
				x -= (1 << i);
				can[j][i] = 1;
			}
		}
		j++;
	}
	vector <int> vec;
	long long res = 0;
	bool ok = 1;
	for(int i = 30; i >= 0; i--){
		int cnt = 0;
		if(vec.empty() && ok){
			for(int j = 0; j < n; j++){
				cnt += can[j][i];
			}
			if(cnt >= k){
				for(int j = 0; j < n; j++){
					if(can[j][i])
						vec.emplace_back(j);
				}
				res += (1 << i);
				ok = 0;
			}
		}
		else{
			vector <int> novi;
			for(int j : vec){
				if(can[j][i]){
					novi.push_back(j);
				}
			}
			if(novi.size() >= k){
				res += (1 << i);
				vec = novi;
			}
		}
	}
	cout << res << endl;
}