import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayDeque; import java.util.Arrays; import java.util.Deque; public class Main { static final int INF = 1000000000; static final long MOD = 1000000007; static final double EPS = 1e-10; public static void main(String args[]) throws IOException { IO io = new IO(); int n = io.getInt(); int a[] = io.getIntArrPrim(); long dp[] = new long[1 << 14]; 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; dp[bit] = Math.max(dp[bit], dp[bit - (1 << i) - (1 << j)] + (a[i] ^ a[j])); } } } System.out.println(dp[(1 << n) - 1]); } } class IO { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); public IO() { } public void println(String str) { System.out.println(str); } public void printArr(Object o[]) { for (int i = 0; i < o.length; i++) { System.out.print(o + " "); } System.out.println(); } public int getInt() throws IOException { return Integer.parseInt(br.readLine()); } public long getLong() throws IOException { return Long.parseLong(br.readLine()); } public double getDouble() throws IOException { return Double.parseDouble(br.readLine()); } public String getLine() throws IOException { return br.readLine(); } public int[] getIntArrPrim() throws IOException { String str[] = br.readLine().split(" "); int a[] = new int[str.length]; for (int i = 0; i < str.length; i++) { a[i] = Integer.parseInt(str[i]); } return a; } public Integer[] getIntArr() throws IOException { String str[] = br.readLine().split(" "); Integer a[] = new Integer[str.length]; for (int i = 0; i < str.length; i++) { a[i] = Integer.parseInt(str[i]); } return a; } public Long[] getLongArr() throws IOException { String str[] = br.readLine().split(" "); Long a[] = new Long[str.length]; for (int i = 0; i < str.length; i++) { a[i] = Long.parseLong(str[i]); } return a; } public long[] getLongArrPrim() throws IOException { String str[] = br.readLine().split(" "); long a[] = new long[str.length]; for (int i = 0; i < str.length; i++) { a[i] = Long.parseLong(str[i]); } return a; } public String[] getStrArr(String split) throws IOException { return br.readLine().split(split); } public char[] getCharArr() throws IOException { return br.readLine().toCharArray(); } public int[][] getIntMap(int w, int h, String split) throws IOException { int a[][] = new int[h][w]; for (int i = 0; i < h; i++) { String str[] = br.readLine().split(split); for (int j = 0; j < w; j++) { a[i][j] = Integer.parseInt(str[j]); } } return a; } public long[][] getLongMap(int w, int h, String split) throws IOException { long a[][] = new long[h][w]; for (int i = 0; i < h; i++) { String str[] = br.readLine().split(split); for (int j = 0; j < w; j++) { a[i][j] = Long.parseLong(str[j]); } } return a; } public double[][] getDoubleMap(int w, int h, String split) throws IOException { double a[][] = new double[h][w]; for (int i = 0; i < h; i++) { String str[] = br.readLine().split(split); for (int j = 0; j < w; j++) { a[i][j] = Double.parseDouble(str[j]); } } return a; } public char[][] getCharMap(int w, int h, String split) throws IOException { char a[][] = new char[h][w]; for (int i = 0; i < h; i++) { String str[] = br.readLine().split(split); for (int j = 0; j < w; j++) { a[i][j] = str[j].charAt(0); } } return a; } }