func_code_string: #include <bits/stdc++.h>   using namespace std;   int n;   int a[100010];   int s[100010];   int solve() {     int ret = 0, top = 0;     for (int i = 0; i < n; i++) {       while (top && a[s[top]] < a[i]) --top;       if (top) ret = max(ret, a[s[top]] ^ a[i]);       s[++top] = i;     }     return ret;   }   int main() {     cin >> n;     for (int i = 0; i < n; i++) cin >> a[i];     reverse(a, a + n);     int ans = solve();     reverse(a, a + n);     ans = max(ans, solve());     cout << ans << endl;     return 0;   }   