#include <bits/stdc++.h>

#define st first
#define nd second
#define pb push_back
#define rep(i, a, b) for(int i = (a); i < (b); ++i)
#define sci(x) int x; cin >> x;
#define scvi(v, n) vector<int> v(n); rep(i, 0, n) cin >> v[i];

using namespace std;

typedef long long ll;
typedef pair<int, int> ii;
typedef vector<int> vi;

vi best_match(vi &a, int k, int c=29) {
    vi b; int m = 1 << c;
    for(int &x : a) {
        if(x & m) b.push_back(x);
    }
    if(((int)b.size()) >= k) {
        if(c > 0)
            return best_match(b, k, c-1);
        else 
            return b;
    } else {
        if(c > 0)
            return best_match(a, k, c-1);
        else 
            return a;
    }
}



int main() {
    ios_base::sync_with_stdio(false); cin.tie(0);

    sci(n);
    sci(k);

    scvi(a, n);
    vi b = best_match(a, k);
    int m = (1<<30)-1;
    for(int &x : b) {
        m &= x;
    }
    cout << m << '\n';


    return 0;
}