#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

void print_bin(ll n) {
    for(int i = 29; i >= 0; i--) {
        cerr << ((n & 1 << i) >> i);
    }
    cerr << endl;
}

int main() {
    ll n, k;
    cin >> n >> k;
    multiset<ll> musicians;
    for(ll i = 0; i < n; i++) {
        ll musician;
        cin >> musician;
        musicians.insert(musician);
    }

    for(int date = 29; date >= 0; date--) {
        ll available = 0;
        for (ll x: musicians) {
            if(x & (1<< date)) {
                available++;
            }
        }
        if(available >= k) {
            for(auto it = musicians.begin(); it != musicians.end(); )
                if(!(*it & (1<< date))) {
                    it = musicians.erase(it);
                }
                else {
                    ++it;
                }
        }
    }

    ll result = 0;

    for(int date = 29; date >= 0; date--) {
        ll available = 0;
        for (ll x: musicians) {
            if(x & (1<< date)) {
                available++;
            }
        }
        if(available >= k) {
            result += 1 << date;
        }
    }
    cout << result << endl;

    return 0;
}