#include<bits/stdc++.h> using namespace std; #define int long long #define REP(i,m,n) for(int i=(m);i<(n);i++) #define rep(i,n) REP(i,0,n) #define pb push_back #define all(a) a.begin(),a.end() #define rall(c) (c).rbegin(),(c).rend() #define mp make_pair #define endl '\n' #define fi first #define se second #define vec vector<ll> #define mat vector<vector<ll> > typedef long long ll; typedef pair<ll,ll> pll; typedef long double ld; const ll inf=1e9+7; const ll mod=998244353; signed main(){ ll n;cin>>n; vector<ll>a(n); rep(i,n)cin>>a[i]; ll ma=0; rep(i,n){ rep(j,n){ ma=max(ma,a[i]^a[j]); } } cout<<ma<<endl; }