#include #define endl "\n" using namespace std; #define ll long long #define ld long double #define rep(i,n) for(int i = 0; i < (int)(n); i++) #define repo(i,n) for(int i = 1; i < (int)(n); i++) #define pb push_back #define mp make_pair #define np next_permutation #define fi first #define se second #define all(x) (x).begin(),(x).end() #define uniq(v) v.erase(unique(v.begin(),v.end()),v.end()) #define lb(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin()) #define ub(v,x) (upper_bound(v.begin(),v.end(),x)-v.begin()) using Pair = pair>; #define pq priority_queue, greater> const ll mod=1000000007; //const ll mod=998244353; const ld pi=acos(-1.0); const ll INF = 1LL<<61; templatebool chmax(T &a, const T &b) { if (abool chmin(T &a, const T &b) { if (b= MOD) val %= MOD; if (val < 0) val += MOD; // 0以上であることを保証 } inline ll toll() { return this->val; } // 代入 void operator=(const mint &r) { this->val = r.val; } void operator=(const ll &r) { *this = mint(r); } // 足し算; 符号反転; 引き算 mint operator+(const mint &r) { ll ans = this->val + r.val; if (ans >= MOD) ans -= MOD; return mint(ans); } mint operator-() { ll ans = MOD - this->val; return mint(ans); } mint operator-(const mint &r) { mint rr = r; return *this + (-rr); } //かけ算; 逆元; わり算 mint operator*(const mint &r) { ll ans = this->val * r.val; return mint(ans); } mint inv() { assert(this->val != 0); if (this->val == 1) return mint(1); mint p, q = *this, m(0), n(1), r, c; p.val = MOD; while (q.val > MAX) { r = p.val % q.val; c = m.val - n.val * (p.val / q.val); p = q, q = r, m = n, n = c; } return n * invs[q.val]; } mint operator/(const mint &r) { return *this * mint(r).inv(); } mint operator%(const mint &r) { return mint(this->val % r.val); } // ++ -- 前付きと後ろ付き void operator++() { ++this->val; } void operator++(int a) { a = 0; this->val++; } void operator--() { --this->val; } void operator--(int a) { a = 0; this->val--; } // 四則演算&代入 void operator+=(const mint &r) { *this = *this + r; } void operator-=(const mint &r) { *this = *this - r; } void operator*=(const mint &r) { *this = *this * r; } void operator/=(const mint &r) { *this = *this / r; } void operator%=(const mint &r) { *this = *this % r; } // べき乗 mint pow(long n) { if (n < 0) return inv().pow(-n); // 逆元の-n乗 else if (n == 0) return mint(1); mint half = pow(n / 2); if (n % 2) return *this * half * half; else return half * half; } mint pow(mint n) { return pow(n.val); } // 順列 mint per(mint _k) { assert(this->val <= MAX); const ll n = this->val, k = _k.val; if (k < 0 || k > n) return 0; if (k == 0) return 1; if (k == n) return facts[n]; return mint(facts[n]) * finvs[n - k]; } // コンビネーション mint com(mint _k) { assert(this->val <= MAX); const ll n = this->val, k = _k.val; if (k < 0 || k > n) return 0; if (k == 0 || k == n) return 1; return mint(facts[n]) * finvs[k] * finvs[n - k]; } // 階乗 mint fact() { assert(this->val <= MAX); return mint(facts[this->val]); } friend bool operator<(const mint &l, const mint &r) { return l.val < r.val; } friend bool operator>(const mint &l, const mint &r) { return l.val > r.val; } friend bool operator==(const mint &l, const mint &r) { return l.val == r.val; } friend bool operator!=(const mint &l, const mint &r) { return !(l.val == r.val); } friend bool operator<=(const mint &l, const mint &r) { return !(l.val > r.val); } friend bool operator>=(const mint &l, const mint &r) { return !(l.val < r.val); } friend ostream &operator<<(ostream &os, const mint &out) { os << out.val; return os; } friend istream &operator>>(istream &is, mint &in) { ll inl; is >> inl; in.val = inl % mint::MOD; return is; } }; // べき乗 inline mint mpow(ll n, ll k) { return mint(n).pow(k); } // 順列 inline mint mper(ll n, ll k) { return mint(n).per(k); } // コンビネーション inline mint mcom(ll n, ll k) { return mint(n).com(k); } // 階乗 inline mint mfac(ll n) { return mint(n).fact(); } // static変数 ll *mint::invs = new ll[MAX+1]; ll *mint::facts = new ll[MAX+1]; ll *mint::finvs = new ll[MAX+1]; ll mint::MOD = (ll)1e9 + 7; //ll mint::MOD = (ll)998244353; //————————————————————————————————————————————————— int main(){ cin.tie(0); ios::sync_with_stdio(false); int n; cin>>n; vector p(n); rep(i,n){ cin>>p[i]; } ll ans=0; rep(i,n){ rep(j,n){ chmax(ans,p[i]^p[j]); } } cout << ans << endl; }