#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]);
	
	auto dfs = [&](auto self, int s, int sum) -> int {
		if (s == ~(~0 << N)) return sum;
		int res = 0, mn = -1;
		REP(i, N) {
			if (s >> i & 1) continue;
			if (mn == -1) mn = i;
			else chmax(res, self(self, s | 1 << mn | 1 << i, sum ^ (A[mn] + A[i])));
		}
		return res;
	};
	
	cout << dfs(dfs, 0, 0) << endl;
}