#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; (i) < (int)(n); ++(i))
#define REP3(i, m, n) for (int i = (m); (i) < (int)(n); ++(i))
#define REP_R(i, n) for (int i = (int)(n)-1; (i) >= 0; --(i))
#define REP3R(i, m, n) for (int i = (int)(n)-1; (i) >= (int)(m); --(i))
#define ALL(x) ::std::begin(x), ::std::end(x)
using namespace std;

int64_t solve(int n, int64_t t, const vector<int64_t>& a) {
    map<int64_t, int64_t> cur;
    cur[t] = 0;
    REP (i, n) {
        map<int64_t, int64_t> prv;
        cur.swap(prv);
        for (auto [x, prv_x] : prv) {
            cur[x & a[i]] = max(cur[x & a[i]], prv_x + abs<int64_t>((x & a[i]) - x));
            cur[x | a[i]] = max(cur[x | a[i]], prv_x + abs<int64_t>((x | a[i]) - x));
        }
    }
    int64_t ans = 0;
    for (auto [x, cur_x] : cur) {
        ans = max(ans, cur_x);
    }
    return ans;
}

// generated by online-judge-template-generator v4.7.1 (https://github.com/online-judge-tools/template-generator)
int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    constexpr char endl = '\n';
    int64_t N;
    int64_t T;
    cin >> N;
    vector<int64_t> A(N);
    cin >> T;
    REP (i, N) { cin >> A[i]; }
    auto ans = solve(N, T, A);
    cout << ans << endl;
    return 0;
}