#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <sstream>
#include <map>
#include <set>
#include <queue>
#include <vector>

using namespace std;

typedef long long int ll;
typedef pair<int, int> pii;

#define PB push_back
#define MP make_pair

#define FOR(prom, a, b) for(int prom = (a); prom < (b); prom++)
#define FORD(prom, a, b) for(int prom = (a); prom > (b); prom--)
#define FORDE(prom, a, b) for(int prom = (a); prom >= (b); prom--)
#define R1(a) do{scanf("%d", &(a));}while(0)
#define R2(a, b) do{scanf("%d%d", &(a), &(b));}while(0)
#define R3(a, b, c) do{scanf("%d%d%d", &(a), &(b), &(c));}while(0)
#define SV(vec) do{int s_v_;scanf("%d", &(s_v_));vec.PB(s_v_);}while(0)
#define MM(co, cim) memset((co), (cim), sizeof((co)))
#define DEB(x) cerr << ">>> " << #x << " : " << x << endl;
#define INF 1000000007

#define MAXB

int n, k, a[200014], maxb, ccand, cand[200014], res, cr;

int is_cand (int x, int bshift)
{
  return x & (1 << bshift);
}

int main ()
{
  R2(n, k);
  FOR(i, 0, n) 
  {
    R1(a[i]);
    cand[i] = 1;
  }
  FORDE(bshift, 29, 0)
  {
    ccand = 0;
    FOR(i, 0, n) if (cand[i] && is_cand(a[i], bshift)) ++ccand;
    if (ccand >= k) 
    {
      FOR(i, 0, n) if (!is_cand(a[i], bshift)) cand[i] = 0;
    }
  }
  res = -1;
  cr = 0;
  FOR(i, 0, n) 
  {
    if (cand[i])
    {
      res = (res < 0 ? a[i] : (res & a[i]));
      if (++cr == k) break;
    }
  }
  printf("%d\n", res);
  
  return 0;
}