#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 1e6 + 5, mod = 1e9 + 7, inf = 1e9 + 7;
const ll INF = 1e18 + 5;
int a[N];
int main() {
  ios ::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  for (int i = 1; i <= n; ++i) cin >> a[i];
  int res = 0;
  for (int lol = 30; lol >= 0; lol--) {
    for (int i = 1; i <= n; ++i) {
      if ((a[i] >> lol) & 1) {
        int f = -1;
        int mx = 0;
        for (int j = i - 1; j >= 1; j--) {
          if ((a[j] >> lol) & 1 || a[j] >= a[i]) {
            f = j + 1;
            break;
          }
          if (j == 1) f = j;
          mx = max(mx, a[j]);
          res = max(res, (mx ^ a[i]));
        }
        int s = -1;
        for (int j = i + 1; j <= n; ++j) {
          if ((a[j] >> lol) & 1 || a[j] >= a[i]) {
            s = j - 1;
            break;
          }
          if (j == n) s = j;
          mx = max(mx, a[j]);
          res = max(res, (mx ^ a[i]));
        }
      }
    }
  }
  cout << res;
  return 0;
}
