Vladik often travels by trains. He remembered some of his trips especially well and I would like to tell you about one of these trips:

Vladik is at initial train station, and now n people (including Vladik) want to get on the train. They are already lined up in some order, and for each of them the city code ai is known (the code of the city in which they are going to).

Train chief selects some number of disjoint segments of the original sequence of people (covering entire sequence by segments is not necessary). People who are in the same segment will be in the same train carriage. The segments are selected in such way that if at least one person travels to the city x, then all people who are going to city x should be in the same railway carriage. This means that they can’t belong to different segments. Note, that all people who travel to the city x, either go to it and in the same railway carriage, or do not go anywhere at all.

Comfort of a train trip with people on segment from position l to position r is equal to XOR of all distinct codes of cities for people on the segment from position l to position r. XOR operation also known as exclusive OR.

Total comfort of a train trip is equal to sum of comfort for each segment.

Help Vladik to know maximal possible total comfort.

Input

First line contains single integer n (1 ≤ n ≤ 5000) — number of people.

Second line contains n space-separated integers a1, a2, ..., an (0 ≤ ai ≤ 5000), where ai denotes code of the city to which i-th person is going.

Output

The output should contain a single integer — maximal possible total comfort.

Examples

Input

6
4 4 2 5 2 3


Output

14


Input

9
5 1 3 1 5 2 4 2 5


Output

9

Note

In the first test case best partition into segments is: [4, 4] [2, 5, 2] [3], answer is calculated as follows: 4 + (2 xor 5) + 3 = 4 + 7 + 3 = 14

In the second test case best partition into segments is: 5 1 [3] 1 5 [2, 4, 2] 5, answer calculated as follows: 3 + (2 xor 4) = 3 + 6 = 9.
import java.io.*;
import java.util.*;

public class ProblemC {

    public static void main(String[] args) throws IOException {
        init();
        new ProblemC().run();
        out.flush();
        out.close();
    }

    static void init() throws IOException {
        in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
        out = new PrintWriter(new OutputStreamWriter(System.out));
        in.ordinaryChars(0, 65535);
        in.wordChars(0, 65535);
        in.whitespaceChars(' ', ' ');
        in.whitespaceChars('\n', '\n');
        in.whitespaceChars('\r', '\r');
    }

    // класс для пар
    class Pair<L, R> {
        private final L X;
        private final R Y;

        public Pair(L X, R Y) {
            this.X = X;
            this.Y = Y;
        }

        public L getX() {
            return X;
        }

        public R getY() {
            return Y;
        }

        @Override
        public int hashCode() {
            return X.hashCode() ^ Y.hashCode();
        }

        @Override
        public boolean equals(Object o) {
            if (!(o instanceof Pair)) return false;
            Pair pairo = (Pair) o;
            return X.equals(pairo.getX()) && Y.equals(pairo.getY());
        }
    }

    static final long INFL = 200000000000000000L;
    static final int INF = 2000000000;
    static final boolean DEBUG = true;

    static StreamTokenizer in;
    static PrintWriter out;

    static void print(String s) {
        print(s, 0);
    }

    static void print(String s, int debug) {
        if (debug == 0 || DEBUG) {
            out.print(s);
        }
    }

    static void println(String s) {
        println(s, 0);
    }

    static void println(String s, int debug) {
        if (debug == 0 || DEBUG) {
            out.println(s);
        }
    }

    static void printArray(int[] arr) {
        println(Arrays.toString(arr));
    }

    static void printArray(char[] arr) {
        println(Arrays.toString(arr));
    }

    static void printArray(String[] arr) {
        println(Arrays.toString(arr));
    }

    static void sort(int[] a) {
        Random rnd = new Random();
        for (int i = a.length - 1; i > 0; i--) {
            int index = rnd.nextInt(i);
            a[i] ^= a[index];
            a[index] ^= a[i];
            a[i] ^= a[index];
        }
        Arrays.sort(a);
    }

    static char[] inChars;
    static int inCharsInd;

    static String next() throws IOException {
        in.nextToken();
        return in.sval;
    }

    static char nextChar() throws IOException {
        while (inChars == null || inCharsInd >= inChars.length) {
            inChars = next().toCharArray();
            inCharsInd = 0;
        }
        return inChars[inCharsInd++];
    }

    static int nextInt() throws IOException {
        return Integer.valueOf(next());
    }

    static double nextDouble() throws IOException {
        return Double.valueOf(next());
    }

    static long nextLong() throws IOException {
        return Long.valueOf(next());
    }

    private void run() throws IOException {
        solve();
    }

    int K, L, M, N, P;
    int[] a;
    int[] first = new int[5010];
    int[] last = new int[5010];


    private void solve() throws IOException {
        N = nextInt();
        a = new int[N];
        for (int i = 0; i < N; i++) {
            a[i] = nextInt();
        }
        findAnswer = new long[a.length];
        Arrays.fill(findAnswer, -1);
        Arrays.fill(last, -1);
        Arrays.fill(first, INF);
        for (int i = 0; i < a.length; i++) {
            last[a[i]] = i;
            first[a[i]] = Math.min(i, first[a[i]]);
        }

        long answer = 0;
        for (int i = a.length - 1; i >= 0; i--) {
            answer = Math.max(answer, findAnswer(i));
        }
        out.println(answer);
    }

    long[] findAnswer;

    private long findAnswer(int index) {
        if (index >= a.length){
            return 0;
        } else if (findAnswer[index] >= 0){
            return findAnswer[index];
        }
        Set<Integer> integerSet = new HashSet<>();
        long answer = 0;
        int curInd = index;
        int lastInd = last[a[curInd]];
        while (curInd <= lastInd){
            if (first[a[curInd]] < index){
                integerSet.clear();
                break;
            }
            integerSet.add(a[curInd]);
            lastInd = Math.max(lastInd, last[a[curInd]]);
            curInd++;
        }

        for (Integer i : integerSet){
            answer ^= i;
        }
        findAnswer[index] = Math.max(answer + findAnswer(lastInd+1), findAnswer(index+1));
        return findAnswer[index];
    }

}