// #pragma GCC optimize("Ofast")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt")
// #define NDEBUG

#include <bits/extc++.h>
#include <x86intrin.h>

struct rep {
  struct iter {
    int i;
    constexpr void operator++() { ++i; }
    constexpr int operator*() const { return i; }
    friend constexpr bool operator!=(iter a, iter b) { return *a != *b; }
  };
  const int l, r;
  constexpr rep(int _l, int _r) : l(std::min(_l, _r)), r(_r) {}
  constexpr rep(int n) : rep(0, n) {}
  constexpr iter begin() const { return {l}; }
  constexpr iter end() const { return {r}; }
};
struct per {
  struct iter {
    int i;
    constexpr void operator++() { --i; }
    constexpr int operator*() const { return i; }
    friend constexpr bool operator!=(iter a, iter b) { return *a != *b; }
  };
  const int l, r;
  constexpr per(int _l, int _r) : l(std::min(_l, _r)), r(_r) {}
  constexpr per(int n) : per(0, n) {}
  constexpr iter begin() const { return {r - 1}; }
  constexpr iter end() const { return {l - 1}; }
};
template <class T, class U>
constexpr bool chmin(T& a, U&& b) {
  return b < a ? a = std::forward<U>(b), true : false;
}
template <class T, class U>
constexpr bool chmax(T& a, U&& b) {
  return a < b ? a = std::forward<U>(b), true : false;
}

int main() {
  using namespace std;
  cin.tie(nullptr)->sync_with_stdio(false);
  int n, x;
  cin >> n >> x;
  vector<int> a(n);
  for (auto&& e : a) cin >> e;
  vector<vector<int>> p(30);
  for (int s : rep(30))
    for (int i : rep(n + 1))
      if (i == n or (a[i] >> s & 1) != ((i ? a[i - 1] : x) >> s & 1))
        p[s].push_back(i);
  int64_t ans{};
  for (int s : rep(30))
    for (int k : rep(1, size(p[s]))) {
      int l = p[s][k - 1], r = p[s][k];
      if (s + 1 < 30 and binary_search(begin(p[s + 1]), end(p[s + 1]), l) and
          binary_search(begin(p[s + 1]), end(p[s + 1]), r) and
          (a[l] >> s & 1) != (a[l] >> (s + 1) & 1))
        continue;
      ans += 1 << s;
    }
  cout << ans << '\n';
}