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.math.*;
import java.security.KeyStore.Entry;
import java.util.*;


 public class Main {
	private InputStream is;
	private PrintWriter out;
	int time = 0, dp[][], DP[], start[], end[], red[], black[], MOD = (int)(1e9+7), arr[];
	int MAX = 200000, N, K;
	ArrayList<Integer>[] amp;
	boolean b[];
	Pair prr[];
	HashSet<Integer> hs = new HashSet<>();

	public static void main(String[] args) throws Exception {
		new Thread(null, new Runnable() {
		public void run() {
			try {

		//new Main().soln();
		} catch (Exception e) {
				System.out.println(e);
			}
		}
	}, "1", 1 << 26).start();
		new Main().soln();
	}
	void solve() {
		int n = ni();
		arr = na(n);
		start = new int[5001];
		end = new int[5001];
		Arrays.fill(start, -1);
		Arrays.fill(end, -1);
		for(int i = 0; i< n; i++){
			if(start[arr[i]]==-1){
				start[arr[i]] = i+1;
			}
		}
		for(int i = n-1; i>=0; i--){
			if(end[arr[i]]==-1){
				end[arr[i]] = i+1;
			}
		}
		for(int i = 0;i<n;i++){
			int min = start[arr[i]], max = end[arr[i]];
			for(int j = start[arr[i]]-1; j<end[arr[i]];j++){
				min = Math.min(start[arr[j]], min);
				max = Math.max(end[arr[j]], max);
			}
			end[arr[i]] = max;
			start[arr[i]] = min;
		}
		for(int i = 0;i<n;i++){
			int min = start[arr[i]], max = end[arr[i]];
			for(int j = start[arr[i]]-1; j<end[arr[i]];j++){
				min = Math.min(start[arr[j]], min);
				max = Math.max(end[arr[j]], max);
			}
			end[arr[i]] = max;
			start[arr[i]] = min;
		}
		for(int i = 0;i<n;i++){
			int min = start[arr[i]], max = end[arr[i]];
			for(int j = start[arr[i]]-1; j<end[arr[i]];j++){
				min = Math.min(start[arr[j]], min);
				max = Math.max(end[arr[j]], max);
			}
			start[arr[i]] = max;
			start[arr[i]] = min;
		}
		red = new int[n+1];
		HashSet<Integer> hs = new HashSet<>();
		for(int i = 0;i<n;i++){
			red[i+1] = red[i];
			if(!hs.contains(arr[i])){
				red[i+1]^=arr[i];
				hs.add(arr[i]);
			}
		}
		int val[] = new int[n+1];
		for(int i = n-1;i>=0;i--){
			int ans1 = 0, fa = 0;
			if(start[arr[i]]>i){
				ans1 = (red[end[arr[i]]]^red[start[arr[i]]-1]);
				fa = ans1;
				for(int j = n-1;j>=end[arr[i]];j--){
					fa = Math.max(ans1+val[j], fa);
				}
			}
			val[i] = Math.max(fa, val[i+1]);
		}
		System.out.println(val[0]);
		//for(int i:val) System.out.println(i);
		//for(int i = 0; i< 6; i++)
			//System.out.println(start[i]+" "+end[i]);
		//for(int i : red) System.out.print(i+" ");
		//DP = new int[n+10];
		//Arrays.fill(DP, -1);
		//N = n;
		//System.out.println(recur(0));
		//for(int i = 0; i<n;i++){
		//	System.out.println(DP[i]);
		//}
	}
	int recur(int n){
		//System.out.println(n);
		if(n>=N) return 0;
		if(DP[n]!=-1) return DP[n];
		int ans = 0;
		DP[n] = 0;
		
		for(int i = n; i<N;i++){
			if(start[arr[i]]>n){
				DP[i] = Math.max((red[end[arr[i]]]^red[start[arr[i]]-1]+recur(end[arr[i]])),DP[i]);
			}
			/*if(start[arr[i]]>i){
				ans = Math.max(ans,(red[end[arr[i]]]^red[start[arr[i]]-1]+recur(end[arr[i]])));
				if(arr[i]==2){
					System.out.println(i);
					System.out.println((red[end[arr[i]]]^red[start[arr[i]]-1])+"*");
					System.out.println(ans);
				}
			}*/
		}
		return DP[n];
	}
	void recur(int n, int k){
		if(k<0) return;
		hs.add(K-k);
		if(n>=0 && dp[n][k]!=-1) return;
		if(n>=0) dp[n][k] = 1;
		for(int i = n+1;i<N;i++){
			recur(i,k-arr[i]);
		}
	}
	long modInverse(long a, long mOD2){
        return  power(a, mOD2-2, mOD2);
	}
	long power(long x, long y, long m)
	{
		if (y == 0)
    return 1;
	long p = power(x, y/2, m) % m;
	p = (p * p) % m;

	return (y%2 == 0)? p : (x * p) % m;
	}
	boolean isPrime(int x){
		for(int i = 2;i*1L*i<=x;i++) if(x%i==0) return false;
		return true;
	}
	public String isPossible(int b[]){
		String ans = "Possible";
		int n = b.length;
		Arrays.sort(b);
		if(n==1) return "Possible";
		if(b[0]==1) return "Impossible";
		if(b[0]>=n) return ans;
		int lcm = 1;
		for(int i : b){
			long gcd = gcd(lcm,i);
			lcm *= (i/gcd);
		}
		int cnt = 0;
		for(int i : b) cnt+=lcm/i;
		if(cnt>lcm) return "Impossible";
		return ans;
	}
	public long gcd(long a, long b){
		if(b==0) return a;
		return gcd(b,a%b);
	}
	void failFn(String str, int arr[]){
		int len = 0;
		arr[0] = 0;
		int i = 1;
		while(i<arr.length){
			if(str.charAt(i)==str.charAt(len)){
				arr[i++] = ++len;
				continue;
			}
			if(len == 0){
				arr[i] = len;
				i++;
				continue;
			}
			if(str.charAt(i)!=str.charAt(len)){
				len = arr[len-1];
			}
		}
	}
	static class ST1{
		int arr[], st[], size;
		ST1(int a[]){
			arr = a.clone();
			size = 10*arr.length;
			st = new int[size];
			build(0,arr.length-1,1);
		}
		void build(int ss, int se, int si){
			if(ss==se){
				st[si] = arr[ss];
				return;
			}
			int mid = (ss+se)/2;
			int val = 2*si;
			build(ss,mid,val); build(mid+1,se,val+1);
			st[si] = Math.min(st[val], st[val+1]);
		}
		int get(int ss, int se, int l, int r, int si){
			if(l>se || r<ss || l>r) return Integer.MAX_VALUE;
			if(l<=ss && r>=se) return st[si];
			int mid = (ss+se)/2;
			int val = 2*si;
			return Math.min(get(ss,mid,l,r,val), get(mid+1,se,l,r,val+1));
		}
	}
	static class ST{
		int arr[],lazy[],n;
		ST(int a){
			n = a;
			arr = new int[10*n];
			lazy = new int[10*n];
		}
		void up(int l,int r,int val){
			update(0,n-1,0,l,r,val);
		}
		void update(int l,int r,int c,int x,int y,int val){
			if(lazy[c]!=0){
				lazy[2*c+1]+=lazy[c];
				lazy[2*c+2]+=lazy[c];
				if(l==r)
					arr[c]+=lazy[c];
				lazy[c] = 0;
			}
			if(l>r||x>y||l>y||x>r)
				return;
			if(x<=l&&y>=r){
				lazy[c]+=val;
				return ;
			}
			int mid = l+r>>1;
			update(l,mid,2*c+1,x,y,val);
			update(mid+1,r,2*c+2,x,y,val);
			arr[c] = Math.max(arr[2*c+1], arr[2*c+2]);
		}
		int an(int ind){
			return ans(0,n-1,0,ind);
		}
		int ans(int l,int r,int c,int ind){
			if(lazy[c]!=0){
				lazy[2*c+1]+=lazy[c];
				lazy[2*c+2]+=lazy[c];
				if(l==r)
					arr[c]+=lazy[c];
				lazy[c] = 0;
			}
			if(l==r)
				return arr[c];
			int mid = l+r>>1;
			if(mid>=ind)
				return ans(l,mid,2*c+1,ind);
			return ans(mid+1,r,2*c+2,ind);
		}
	}
	public static class FenwickTree {
		
	    int[] array; // 1-indexed array, In this array We save cumulative information to perform efficient range queries and updates

	    public FenwickTree(int size) {
	        array = new int[size + 1];
	    }
	    public int rsq(int ind) {
	        assert ind > 0;
	        int sum = 0;
	        while (ind > 0) {
	            sum += array[ind];
	            //Extracting the portion up to the first significant one of the binary representation of 'ind' and decrementing ind by that number
	            ind -= ind & (-ind);
	        }
	        return sum;
	    }
	    public int rsq(int a, int b) {
	        assert b >= a && a > 0 && b > 0;
	        return rsq(b) - rsq(a - 1);
	    }
	    public void update(int ind, int value) {
	        assert ind > 0;
	        while (ind < array.length) {
	            array[ind] += value;
	            //Extracting the portion up to the first significant one of the binary representation of 'ind' and incrementing ind by that number
	            ind += ind & (-ind);
	        }
	    }
	    public int size() {
	        return array.length - 1;
	    }
	}
	public static int[] shuffle(int[] a, Random gen){
		for(int i = 0, n = a.length;i < n;i++)
		{ 
			int ind = gen.nextInt(n-i)+i; 
			int d = a[i]; 
			a[i] = a[ind];
			a[ind] = d; 
		} 
	return a; 
	}

	class Pair implements Comparable<Pair>{
		int u, v;
		Pair(int u, int v){
			this.u = u;
			this.v = v;
		}public int hashCode() {
			return Objects.hash();
		}
		public boolean equals(Object o) {
			Pair other = (Pair) o;
			return ((u == other.u && v == other.v) || (v == other.u && u == other.v));
		}
		public int compareTo(Pair other) {
			//return Integer.compare(val, other.val);
			return Long.compare(u, other.u);// != 0 ? (Long.compare(u, other.u)) : (Long.compare(v,other.v));
		}
	}
	long power(long x, long y, int mod){
		long ans = 1;
		while(y>0){
			if(y%2==0){
				x = (x*x)%mod;
				y/=2;
			}
			else{
				ans = (x*ans)%mod;
				y--;
			}
		}
		return ans;
	}
	void soln() {
		is = System.in;
		out = new PrintWriter(System.out);
		long s = System.currentTimeMillis();
		solve();
		//out.close();
		out.flush();
		//tr(System.currentTimeMillis() - s + "ms");
	}


	// To Get Input
	// Some Buffer Methods
	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;

	private int readByte() {
		if (lenbuf == -1)
			throw new InputMismatchException();
		if (ptrbuf >= lenbuf) {
			ptrbuf = 0;
			try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		}
		return inbuf[ptrbuf++];
	}

	private boolean isSpaceChar(int c) {
		return !(c >= 33 && c <= 126);
	}

	private int skip() {
		int b;
		while ((b = readByte()) != -1 && isSpaceChar(b))
			;
		return b;
	}

	private double nd() {
		return Double.parseDouble(ns());
	}

	private char nc() {
		return (char) skip();
	}
	private String ns() {
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != '
									// ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}

	private char[] ns(int n) {
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while (p < n && !(isSpaceChar(b))) {
			buf[p++] = (char) b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}

	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for (int i = 0; i < n; i++)
			map[i] = ns(m);
		return map;
	}

	private int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	}

	private int ni() {
		int num = 0, b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private long nl() {
		long num = 0;
		int b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private boolean oj = System.getProperty("ONLINE_JUDGE") != null;

	private void tr(Object... o) {
		if (!oj)
			System.out.println(Arrays.deepToString(o));
	}
}