#include <iostream>
#include <vector>

using namespace std;

long long N, K, ans, a;
vector<long long> el;
vector<long long> uj;
long long hat[31];

int main()
{
    ios_base::sync_with_stdio(false);
    cin >> N >> K;
    for(int i=0; i<N; i++){
        cin >> a;
        el.push_back(a);
    }

    hat[0] = 1;
    for(int i=1; i<=30; i++) hat[i] = 2*hat[i-1];

    for(int i=30; i>=0; i--){
        uj.clear();
        for(long long j:el){
            if((j&hat[i])!=0) uj.push_back(j);
        }
        if(uj.size()>=K){
            ans += hat[i];
            el.clear();
            for(long long j:uj) el.push_back(j);
        }
    }

    cout << ans << endl;

    return 0;
}