#include <bits/stdc++.h>
using namespace std;
const int N = 1e6;
int n, t[1000001];
struct data {
  int num, loc, vis;
} b[1000001];
int a[1000001];
int lowbit(int x) { return x & (-x); }
int Query(int x) {
  int sum = 0;
  while (x > 0) {
    sum = max(sum, t[x]);
    x -= lowbit(x);
  }
  return sum;
}
void Add(int x, int va) {
  while (x <= N) {
    t[x] = max(t[x], va);
    x += lowbit(x);
  }
}
bool cmp(data p, data q) { return p.num < q.num; }
bool cmp2(data p, data q) { return p.vis < q.vis; }
int work() {
  memset(t, 0, sizeof(t));
  for (int i = 1; i <= n; i++) {
    b[i].num = a[i];
    b[i].vis = i;
  }
  sort(b + 1, b + n + 1, cmp);
  for (int i = 1; i <= n; i++) b[i].loc = n + 1 - i;
  sort(b + 1, b + n + 1, cmp2);
  int ans = 0;
  for (int i = 1; i <= n; i++) {
    int nowans = Query(b[i].loc);
    Add(b[i].loc, i);
    if (nowans == 0) continue;
    ans = max(ans, b[i].num ^ b[nowans].num);
  }
  return ans;
}
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
  int ans = work();
  for (int i = 1; i <= n / 2; i++) swap(a[i], a[n + 1 - i]);
  ans = max(ans, work());
  printf("%d\n", ans);
  return 0;
}
