#include <iostream>
#include <vector>

constexpr int INF = 1 << 30;

void solve() {
    int n;
    std::cin >> n;
    std::vector<int> xs(n);
    for (auto& x : xs) std::cin >> x;

    std::vector<int> dp(1 << n, -INF);
    dp[0] = 0;

    for (int b = 0; b < (1 << n) - 1; ++b) {
        int i = 0;
        while ((b >> i) & 1) ++i;
        for (int j = i + 1; j < n; ++j) {
            if ((b >> j) & 1) continue;

            int y = xs[i] ^ xs[j];
            int nb = b | (1 << i) | (1 << j);
            dp[nb] = std::max(dp[nb], dp[b] + y);
        }
    }

    std::cout << dp.back() << "\n";
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}