#include <iostream>
#include <stdio.h>
#include <cmath>
#include <algorithm>
#include <memory>
#include <map>

int melyik_nap_mennyi[30][200000];
int melyik_nap_meret[30];

using namespace std;

    int ketto_hatvany[] = {
        1,
        2,
        4,
        8,
        16,
        32,
        64,
        128,
        256,
        512,
        1024,
        2048,
        4096,
        8192,
        16384,
        32768,
        65536,
        131072,
        262144,
        524288,
        1048576,
        2097152,
        4194304,
        8388608,
        16777216,
        33554432,
        67108864,
        134217728,
        268435456,
        536870912
    };

void magic(int band, int temp) {
    for (int i = 29; i >= 0; i--) {
        if (temp >= ketto_hatvany[i]) {
            temp -= ketto_hatvany[i];

            melyik_nap_mennyi[i][melyik_nap_meret[i]] = band;
            melyik_nap_meret[i]++;
        }
    } 
}

int n, k;
map<int, bool> aktual_map;

int main() {

    cin >> n >> k;

    for (int i = 0; i < 30; i++) {
        melyik_nap_meret[i] = 0;
    }

    int temp;
    for (int i = 0; i < n; i++) {
        scanf("%d", &temp);
        magic(i, temp);
    }

/*
    for (int i = 0; i < 30; i++) {
        for (int j = 0; j < melyik_nap_meret[i]; j++) {
            cout << melyik_nap_mennyi[i][j] << " ";
        }
        cout << endl;
    }
*/
    bool found_first = false;
    int result = 0;
    int index_ = 0;

    for (int i = 29; i >= 0; i--) {
        if (melyik_nap_meret[i] >= k) {
            for (int j = 0; j < melyik_nap_meret[i]; j++) {
                aktual_map[melyik_nap_mennyi[i][j]] = true;
            }
            result += ketto_hatvany[i];

            index_ = i;
            break;
        }
    }

    for (int i = index_ - 1; i >= 0; i--) {
        int counter = 0;
        map<int, bool> next_aktual;

        if (melyik_nap_meret[i] >= k) {
            for (int j = 0; j < melyik_nap_meret[i]; j++) {
                if (aktual_map[melyik_nap_mennyi[i][j]]) {
                    next_aktual[melyik_nap_mennyi[i][j]] = true;
                    counter++;
                }
            }
            
            if (counter >= k) {
                aktual_map = next_aktual;
                result += ketto_hatvany[i];
            }
        }
    }
    cout << result << endl;
    return 0;
}