#include #pragma GCC target("avx2") #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") using namespace std; /*----------------------------------ここからマクロ----------------------------------*/ #define all(a) (a).begin(),(a).end() #define rall(a) (a).rbegin(),(a).rend() #define vecin(a) rep(i,a.size())cin >> a[i] #define overload4(_1,_2,_3,_4,name,...) name /*#define rep1(n) for(int i=0;i<(int)n;++i) #define rep2(i,n) for(int i=0;i<(int)n;++i) #define rep3(i,a,b) for(int i=(int)a;i<(int)b;++i) #define rep4(i,a,b,c) for(int i=(int)a;i<(int)b;i+=(int)c)*/ #define rep1(n) for(ll i=0;i<(ll)n;++i) #define rep2(i,n) for(ll i=0;i<(ll)n;++i) #define rep3(i,a,b) for(ll i=(ll)a;i<(ll)b;++i) #define rep4(i,a,b,c) for(ll i=(ll)a;i<(ll)b;i+=(ll)c) #define rep(...) overload4(__VA_ARGS__,rep4,rep3,rep2,rep1)(__VA_ARGS__) #ifdef _DEBUG #define debug1(a) cerr << #a << ": " << a << "\n" #define debug2(a,b) cerr << #a << ": " << a << ", " << #b << ": " << b << "\n" #define debug3(a,b,c) cerr << #a << ": " << a << ", " << #b << ": " << b << ", " << #c << ": " << c << "\n" #define debug4(a,b,c,d) cerr << #a << ": " << a << ", " << #b << ": " << b << ", " << #c << ": " << c << ", " << #d << ": " << d << "\n" #define debug(...) overload4(__VA_ARGS__,debug4,debug3,debug2,debug1)(__VA_ARGS__) #define vecout(a) cerr << #a << ": [";rep(i,a.size()){cerr << a[i];cerr << (i == a.size() - 1 ? "":",");}cerr << "]\n" #else #define debug(...) #define vecout(a) #endif #define mp make_pair #define fi first #define se second //struct doset{doset(int n){cout << fixed << setprecision(n);cerr << fixed << setprecision(n);}}; //struct myset{myset(){ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);}}; void myset(){ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);} void doset(int n){cout << fixed << setprecision(n);cerr << fixed << setprecision(n);} void koko(){cerr << "koko\n";} using ll = long long; using ld = long double; using dou = double; const int inf = 1 << 30; const ll INF = 1LL << 61; const ld pi = 3.14159265358; const ll mod1 = 1000000007LL; const ll mod2 = 998244353LL; typedef pair P; template inline bool chmin(T& a, const U& b){ if(a > b){ a = b; return 1; } return 0; } template inline bool chmax(T& a, const U& b){ if(a < b){ a = b; return 1; } return 0; } //nのm乗をMODで割ったあまりO(logm) ll modpow(ll n,ll m,ll MOD){ if(m == 0)return 1; if(m < 0)return 0; ll res = 1; n %= MOD; while(m){ if(m & 1)res = (res * n) % MOD; m >>= 1; n *= n; n %= MOD; } return res; } ll mypow(ll n,ll m){ if(m == 0)return 1; if(m < 0)return -1; ll res = 1; while(m){ if(m & 1)res = (res * n); m >>= 1; n *= n; } return res; } //素数判定O(sqrt(N)) template inline bool isp(T n){ bool res = true; if(n == 1 || n == 0)return false; else{ for(ll i = 2;i * i <= n;i++){ if(n % i == 0){ res = false; break; } } return res; } } inline bool Yes(bool b = 1){cout << (b ? "Yes\n":"No\n");return b;} inline bool YES(bool b = 1){cout << (b ? "YES\n":"NO\n");return b;} map primefactor(ll n){ map ma; if(n <= 1)return ma; ll m = n; for(ll i = 2;i * i <= n;i++){ while(m % i == 0){ ma[i]++; m /= i; } } if(m != 1)ma[m]++; return ma; } ll __lcm(ll a,ll b){ return a / __gcd(a,b) * b; } inline void in(){return;} templateinline void in(First& F,Other&...O){cin >> F;in(O...);} template struct fac_solver{ private: ll cmax; vector fac,finv,inv; public: fac_solver(ll n = 100000):cmax(n),fac(n),finv(n),inv(n){ fac[0] = fac[1] = 1; finv[0] = finv[1] = 1; inv[1] = 1; for (ll i = 2; i < cmax; i++){ fac[i] = fac[i - 1] * i % MOD; inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD; finv[i] = finv[i - 1] * inv[i] % MOD; } } //二項係数計算nCk ll COM(ll n, ll k){ if (n < k) return 0; if (n < 0 || k < 0) return 0; return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD; } ll PER(ll n,ll k){ if(n < k || n < 0 || k < 0)return 0; return fac[n] * finv[n - k] % MOD; } ll stair_pow(ll n){return fac[n];} }; /*----------------------------------マクロここまで----------------------------------*/ int main(){ myset(); int N; cin >> N; vector vec(N); rep(i,N)cin >> vec[i]; int ans = 0; rep(i,N){ rep(j,i + 1,N)chmax(ans,vec[i] ^ vec[j]); } cout << ans << "\n"; }