#include <bits/stdc++.h>
using namespace std;
template <class T>
T abs(T x) {
  return x > 0 ? x : -x;
}
int n;
int m;
vector<int> v;
int x[100000];
int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", &x[i]);
  for (int i = 29; i >= 0; i--) {
    v.clear();
    for (int j = 0; j < n; j++)
      if ((x[j] >> i) & 1) v.push_back(j);
    if (((int)(v).size()) > 0 && ((int)(v).size()) < n) {
      int ans = 0;
      for (int j = 0; j < ((int)(v).size()); j++) {
        int cur = 0;
        int tmp = 0;
        if (j > 0) tmp = v[j - 1] + 1;
        for (int k = v[j] - 1; k >= tmp; k--) {
          cur = max(cur, x[k]);
          ans = max(ans, cur ^ x[v[j]]);
        }
        cur = 0;
        tmp = n - 1;
        if (j + 1 < ((int)(v).size())) tmp = v[j + 1] - 1;
        for (int k = v[j] + 1; k <= tmp; k++) {
          cur = max(cur, x[k]);
          ans = max(ans, cur ^ x[v[j]]);
        }
      }
      printf("%d\n", ans);
      break;
    }
  }
  return 0;
}
