#include<bits/stdc++.h>
using namespace std;

#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()
#define rep(i,n,m) for(int i = (n); i < (int)(m); i++)
#define rrep(i,n,m) for(int i = (m) - 1; i >= (int)(n); i--)
using ll = long long;
using ld = long double;
const ll MOD1 = 1e9+7;
const ll MOD9 = 998244353;
const int INF = (int)1e9+1;
template<typename T>
bool chmin(T &a,T b){if(a>b){a=b;return true;}else return false;}
template<typename T>
bool chmax(T &a,T b){if(a<b){a=b;return true;}else return false;}
template<typename T>
vector<ll>dx={1,0,-1,0,1,1,-1,-1};
vector<ll>dy={0,1,0,-1,1,-1,1,-1};
pair<int,ll> ope(pair<int,ll> now,int val,int cmd){
  if(cmd==0)return make_pair(now.first|val,now.second+abs((now.first|val)-now.first));
  if(cmd==1)return make_pair(now.first&val,now.second+abs((now.first&val)-now.first));
}
ll solve1(ll n,ll t,vector<int>&a){
  pair<int,ll>p(t,0);
  rep(i,0,n){
    auto nxt0=ope(p,a[i],0);
    auto nxt1=ope(p,a[i],1);
    if(nxt0.second<nxt1.second)swap(nxt0,nxt1);
    p=nxt0;
  }
  return p.second;
}
ll solve4(ll n,ll t,vector<int>&a){
  pair<int,ll>p(t,0);
  rep(i,0,n){
    auto nxt0=ope(p,a[i],1);
    auto nxt1=ope(p,a[i],0);
    if(nxt0.second<nxt1.second)swap(nxt0,nxt1);
    p=nxt0;
  }
  return p.second;
}
ll solve2(ll n,ll t,vector<int>&a){
  pair<int,ll>p(t,0);
  rep(i,0,n){
    p=ope(p,a[i],i&1);
  }
  return p.second;
}
ll solve3(ll n,ll t,vector<int>&a){
  pair<int,ll>p(t,0);
  rep(i,0,n){
    p=ope(p,a[i],~i&1);
  }
  return p.second;
}

int main(){
  int n,t;
  cin>>n>>t;
  vector<int>a(n);
  rep(i,0,n)cin>>a[i];
  ll ret=0;
  chmax(ret,solve1(n,t,a));
  chmax(ret,solve2(n,t,a));
  chmax(ret,solve3(n,t,a));
  chmax(ret,solve4(n,t,a));
  cout<<ret<<endl;
  return 0;
}