#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

#define rep(i, n) for (int i = 0; i < (n); i++)

int main(void){
	int n, k; cin >> n >> k;
    vector<int> cisla(n);
    for (int& i : cisla) cin >> i;
    for (int bit = 29; bit >= 0; bit--) {
        vector<int> c2;
        for (int i : cisla) if (i & (1<<bit)) c2.push_back(i);
        if (c2.size() >= k) cisla = c2;
    }
    int ans = -1;
    for (int i : cisla) ans &= i;
    cout << ans << endl;
}