#include <bits/stdc++.h>
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define REP(i, n)  for(int i=0;i<(n);++i)
#define REPr(i, n) for(int i=(n)-1;i>=0; --i)
#define FORq(i, m, n) for(int i = (m);i <= (n);++i)
#define FORqr(i, m, n) for(int i = (n);i >=(m);--i)
#define PB push_back
#define MP make_pair
#define DEBUG printf("%s\n","debug")
#define fst first
#define snd second
#define SIN(x, S) (S.count(x) != 0)
#define M0(x) memset(x,0,sizeof(x))
#define FILL(x, y) memset(x,y,sizeof(x))
#define MM(x) memset(x,-1,sizeof(x))
#define ALL(x) (x).begin(),(x).end()
#define pfd(n) printf("%d\n",n);
#define pflld(n) printf("%lld\n",n);
#define SCD(n) scanf("%d",&n)
#define SCD2(m,n) scanf("%d%d",&m,&n)
#define SCD3(m,n,k) scanf("%d%d%d",&m,&n,&k)
#define SCLLD(n) scanf("%lld",&n)
#define SCLLD2(m,n) scanf("%lld %lld",&m,&n)
#define SCLLD3(m,n,k) scanf("%lld %lld %lld",&m,&n,&k)
#define DB(x) cerr << #x << " = " << x << endl
#define DB2(x, y) cerr << "(" << #x << ", " << #y << ") = (" << x << ", " << y << ")\n";

using namespace std;
typedef pair<int, int> PII;
typedef pair<long long, long long> PLL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<long long> VL;
typedef long long ll;
typedef long long integer;
///////////////////////////////////////////////
const ll MOD = 1e9+7;
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }
template<class T>
inline bool chmin(T &a, T b) {
	if (a > b) {
		a = b;
		return true;
	}
	return false;
}
template<class T>
inline bool chmax(T &a, T b) {
	if (a < b) {
		a = b;
		return true;
	}
	return false;
}

template<int MOD> struct Fp {
	long long val;
	constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
		if (val < 0) v += MOD;
	}
	constexpr int getmod() { return MOD; }
	constexpr Fp operator - () const noexcept {
		return val ? MOD - val : 0;
	}
	constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
	constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
	constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
	constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
	constexpr Fp& operator += (const Fp& r) noexcept {
		val += r.val;
		if (val >= MOD) val -= MOD;
		return *this;
	}
	constexpr Fp& operator -= (const Fp& r) noexcept {
		val -= r.val;
		if (val < 0) val += MOD;
		return *this;
	}
	constexpr Fp& operator *= (const Fp& r) noexcept {
		val = val * r.val % MOD;
		return *this;
	}
	constexpr Fp& operator /= (const Fp& r) noexcept {
		long long a = r.val, b = MOD, u = 1, v = 0;
		while (b) {
			long long t = a / b;
			a -= t * b; swap(a, b);
			u -= t * v; swap(u, v);
		}
		val = val * u % MOD;
		if (val < 0) val += MOD;
		return *this;
	}
	constexpr bool operator == (const Fp& r) const noexcept {
		return this->val == r.val;
	}
	constexpr bool operator != (const Fp& r) const noexcept {
		return this->val != r.val;
	}
	friend constexpr ostream& operator << (ostream &os, const Fp<MOD>& x) noexcept {
		return os << x.val;
	}
	friend constexpr istream& operator >> (istream &is, Fp<MOD>& x) noexcept {
		return is >> x.val;
	}
	friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
		if (n == 0) return 1;
		auto t = modpow(a, n / 2);
		t = t * t;
		if (n & 1) t = t * a;
		return t;
	}
};
using mint = Fp<MOD>;

/*
template<typename T>
void in( T &x ) { cin>>x; }
void in( int &x ) { scanf("%d",&x); }
void in( long long &x ) { scanf("%" PRId64,&x); }
void in( double &x ) { scanf("%lf",&x); }
void in( char &x ) { scanf(" %c",&x); }
void in( char *x ) { scanf("%s",x); }

template<typename T>
void out( T &x ) { cout<<x; }
void out( int &x ) { printf("%d",x); }
void out( long long &x ) { printf("%" PRId64,x); }
void out( double &x ) { printf("%lf",x); }
void out( char &x ) { printf(" %c",x); }
void out( char *x ) { printf("%s",x); }

void spout(){printf(" ");}
void outn(){printf("\n");}
*/

void scdvec(vector<int> &a,int n,int s = 0){
	for (int i = s; i < n; ++i) {scanf("%d",&a[i]);}
}

void sclldvec(vector<long long> &a,int n,int s = 0){
	for (int i = s; i < n; ++i) {scanf("%lld",&a[i]);}
}

///////////////////////////////////////////////
int main(){
	int N;
	SCD(N);

	vector<int> a(N);
	scdvec(a,N);

	vector<int> dp(1 << N);

	REP(b,1 << N){
		REP(i,N){ //bit loop
			REP(j,N){
				if (i >= j) continue;
				if (b & (1<<i)) continue;
				if (b & (1<<j)) continue;
				chmax(dp[b+(1<<i)+(1<<j)],dp[b] + (a[i] xor a[j]));
			}
		}
	}

	pfd(dp[(1 << N) - 1]);

	return 0;
}