import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		int n = Integer.parseInt(br.readLine());

		long a[] = new long[n];

		String str[] = br.readLine().split(" ");
		for (int i = 0; i < n; i++) {
			a[i] = Long.parseLong(str[i]);
		}

		long dp[] = new long[1 << n];

		dp[0] = 0;

		for (int bit = 0; bit < (1 << n); bit++) {
			for (int i = 0; i < n; i++) {
				if (((bit & (1 << i)) == 0))
					continue;

				for (int j = i + 1; j < n; j++) {
					if (((bit & (1 << j)) == 0))
						continue;

					long t = dp[bit - (1 << i) - (1 << j)] + (a[i] ^ a[j]);
					dp[bit] = Math.max(dp[bit], t);
				}
			}
		}

		System.out.println(dp[(1 << n) - 1]);
	}
}