#include <bits/stdc++.h>

#ifdef LOCAL
#include "../algo/debug.h"
#else 
#define debug(...) 0
#endif

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  long long k;
  cin >> n >> k;
  vector<long long> a(n);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  long long ans = 0, w = 0;
  for (int b = 40; b >= 0; b--) {
    long long now[2] {};
    for (int i = 0; i < n; i++) {
      if (a[i] >> b & 1) {
        now[0] += 1ll << b;
      } else {
        now[1] += 1ll << b;
      }
    }
    if (w + (1ll << b) <= k) {
      if (now[1] > now[0]) {
        w += 1ll << b;
        ans += now[1];
      } else {
        ans += now[0];
      }
    } else {
      ans += now[0];
    }
  }
  cout << ans << '\n';
  return 0;
}