#include<cstdio>
#include<queue>
#include<utility>
#include<cstring>
#include<stack>
#include<algorithm>
#include<cmath>
#include<iostream>
#include<map>
#include<set>
#include<vector>
#define MAX_N 100001
#define INF_INT 2147483647
#define INF_LL 9223372036854775807
#define REP(i,n) for(int i=0;i<(int)(n);i++)
void init(int n);
int find(int n);
void unite(int x,int y);
bool same(int x, int y);
int dx[4] = {1,0,0,-1};
int dy[4] = {0,1,-1,0};
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> P;
bool cmp_P(const P &a,const P &b){
  return a.second < b.second;
}
int N,A[15];


int solve(vector<int> sets){
  int m = -1;
  
  if(sets.size() == 0)
    return 0;
  else{
    for(int i=0;i<sets.size();i++)
      for(int j=i+1;j<sets.size();j++){
        int a=sets[i],b=sets[j];
        sets.erase(sets.begin()+i);
        sets.erase(sets.begin()+j-1);
        m = max(m,(a ^ b) + solve(sets));
        sets.push_back(a);
        sets.push_back(b);
        sort(sets.begin(),sets.end());
      }
    }
  return m;
}

int main()
{
  int N,A;
  cin >> N;
  vector<int> sets(0);
  REP(i,N){
    cin >> A;
    sets.push_back(A);
  }
  sort(sets.begin(),sets.end());
  cout << solve(sets) << endl;
  return 0;
}

int par[MAX_N];
int ranks[MAX_N];

//n要素で初期化
void init(int n){
  REP(i,n){
    par[i] = i;
    ranks[i] = 0;
  }

}

//木の根を求める
int find(int x){
  if(par[x] == x){
    return x;
  }else{
    return par[x] = find(par[x]);
  }
}

void unite(int x,int y){
  x = find(x);
  y = find(y);
  if(x == y) return ;
  if(ranks[x] < ranks[y]){
    par[x] = y;
  }else{
    par[y] = x;
    if(ranks[x] == ranks[y]) ranks[x]++;
  }
}

bool same(int x, int y){
  return find(x) == find(y);
}