import java.io.*;
import java.util.*;
import java.util.Map.*;


public class Main_yukicoder698 {

	private static Scanner sc;
	private static Printer pr;

	private static void solve() {
		int n = sc.nextInt();

		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}

		Map<Integer, Long> hm = new HashMap<>();

		// nn個のビットのうち、ii個のビットが立っているmaskのパターンの生成
		int nn = n;
		int ii = 2;

		int mask = (0x1 << ii) - 1;
		while (mask < 0x1 << nn) {
			// maskに対する処理

			long tmp = 0;
			for (int j = 0; j < n; j++) {
				if ((mask & 0x1 << j) != 0) {
					tmp ^= a[j];
				}
			}
			
			hm.put(mask, tmp);

			// 次のmaskの計算
			int xx = mask & -mask;
			int yy = mask + xx;
			mask = ((mask & ~yy) / xx >> 1) | yy;
		}

		
		Map<Integer, Long> hm2 = new HashMap<>(hm);
		for (int i = 4; i <= n; i += 2) {
			Map<Integer, Long> hmtmp = new HashMap<>();
			for (Entry<Integer, Long> e : hm.entrySet()) {
				int key = e.getKey();
				long value = e.getValue();
				for (Entry<Integer, Long> ee : hm2.entrySet()) {
					int nkey = key | ee.getKey();
					if (Integer.bitCount(nkey) != i) {
						continue;
					}
					
					if (!hmtmp.containsKey(nkey)) {
						hmtmp.put(nkey, 0L);
					}
					hmtmp.put(nkey, Math.max(hmtmp.get(nkey), value + hm2.get(ee.getKey())));
				}
			}
			
			hm2 = hmtmp;
		}
		
		pr.println(hm2.get((0x1 << n) - 1));
	}

	// ---------------------------------------------------
	public static void main(String[] args) {
		sc = new Scanner(INPUT == null ? System.in : new ByteArrayInputStream(INPUT.getBytes()));
		pr = new Printer(System.out);

		solve();

//		pr.close();
		pr.flush();
//		sc.close();
	}

	static String INPUT = null;

	private static class Printer extends PrintWriter {
		Printer(OutputStream out) {
			super(out);
		}
	}
}