#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using ld=double;
#define FOR(i,a,b) for(ll i=a;i<(ll)b;++i)
#define F(n) FOR(i,0,n)
#define FF(n) FOR(j,0,n)
#define aa first
#define bb second
#define PB push_back
#define EQ(a,b) (fabs(a-b)<=(fabs(a+b)*EPS))
#define MOD ((ll)(1e9+7))
#define INF (1ll << 40)

int main() {
  ios::sync_with_stdio(0);cin.tie(0);
  ll n, k;
  cin >> n >> k;
  vector<ll> a(n);
  F(n) {
    cin >> a[i];
  }
  ll bot = 0, top = INF;
  while (bot < top) {
    ll mid = (bot+top+1)/2;
    ll cnt = 0;
    F(n) {
      if ((a[i] & mid) >= mid) cnt ++;
    }
    if (cnt >= k) bot = mid;
    else top = mid - 1;
  }
  cout << bot << endl;

  return 0;
}