#include <bits/stdc++.h> #pragma GCC target("avx") #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") using namespace std; #define ll long long #define INF 9999999999999999 #define rep(i,m,n) for(ll i = m;i < n;i++) #define rrep(i,m,n) for(ll i=m-1;i>=n;i--) #define pb(n) push_back(n) #define UE(N) N.erase(unique(N.begin(),N.end()),N.end()); #define Sort(n) sort(n.begin(), n.end()) #define Rev(n) reverse(n.begin(),n.end()) #define Out(S) cout << S << endl #define NeOut(S) cout << S #define HpOut(S) cout << setprecision(50) << S << endl #define Vec(K,L,N,S) vector<L> K(N,S) #define DV(K,L,N,M,S) vector<vector<L>> K(N,vector<L>(M,S)) #define TV(K,L,N,M,R,S) vector<vector<vector<L>>> K(N,vector<vector<L>>(M,vector<L>(R,S))) #define pint pair<lli,lli> #define tint tuple<int, int, int> #define paf(L,R) pair<L,R> #define mod 998244353 #define MAX 10000010 #define ALL(a) a.begin(),a.end() #define chmax(a, b) a = (((a)<(b)) ? (b) : (a)) #define chmin(a, b) a = (((a)>(b)) ? (b) : (a)) int main() { ios::sync_with_stdio(false); cin.tie(0); ll N, res = 0; cin >> N; vector<ll> A(N); rep(i, 0, N) cin >> A[i]; rep(i, 0, N)rep(j, 0, N) chmax(res, A[i] ^ A[j]); cout << res << endl; }