#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

int main() {
	int N;
	cin >> N;
	vector<int> A(N);
	REP(i, N) scanf("%d", &A[i]);
	vector<int> dp(1 << N, 0);
	REP(i, 1 << N) {
		int mnb = -1;
		REP(j, N) if (~i >> j & 1) { mnb = j; break; }
		if (mnb == -1) continue;
		FOR(j, mnb + 1, N) if (~i >> j & 1) chmax(dp[i | 1 << mnb | 1 << j], dp[i] + (A[mnb] ^ A[j]));
	}
	cout << dp[~(~0 << N)] << endl;
}