#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;
//---------------------------------//

/**
 * @brief https://tkmst201.github.io/Library/Mathematics/bit_operation.hpp
 */
namespace tk {
constexpr int pop_count(std::uint32_t x) {
	x = (x & 0x55555555) + ((x >> 1) & 0x55555555);
	x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
	x = (x + (x >> 4)) & 0x0f0f0f0f;
	x += x >> 8;
	x += x >> 16;
	return x & 0xff;
}

constexpr int count_trailing_zeros(std::uint32_t x) {
	return pop_count(~x & (x - 1));
}
} // namespace tk


int main() {
	int N;
	cin >> N;
	vector<int> A(N);
	REP(i, N) scanf("%d", &A[i]);
	
	int ans = 0;
	auto dfs = [&](auto self, int s, int sum) {
		if (s == ~(~0 << N)) {
			chmax(ans, sum);
			return;
		}
		int cur = ~s & ~(~0 << N);
		const int mn = tk::count_trailing_zeros(cur);
		s |= 1 << mn;
		cur ^= 1 << mn;
		const int pcnt = tk::pop_count(cur);
		if (pcnt >= 6) {
			REP(i, N) if (~s >> i & 1) self(self, s | 1 << i, sum ^ (A[mn] + A[i]));
		}
		else {
			while (cur > 0) {
				const int b = tk::count_trailing_zeros(cur);
				self(self, s | 1 << b, sum ^ (A[mn] + A[b]));
				cur ^= 1 << b;
			}
		}
	};
	
	dfs(dfs, 0, 0);
	cout << ans << endl;
}