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.BigInteger;
import java.text.DecimalFormat;
import java.util.*;
 
 
 
     
     
    public  class Main {
    	public static InputReader in;
        public static PrintWriter pw;
     
     
     
    	public static void main(String args[]) 
    	{
    		new Thread(null, new Runnable() {
                public void run() {
                    try{
                        solve();
                    }
                    catch(Exception e){
                        e.printStackTrace();
                    }
                }
            }, "1", 1 << 26).start();
        }
    	static ArrayList<Integer> g[];
    	static ArrayList<Integer> h[];
    	static boolean visited[];
    	static int[] parent;
    	static int par[];
    	static int degree[];
    	static int edjes=0;
    	static int start=-1;
    	static int end=-1;
    	static int Total=0;
    	static int time1[];
    	static int time2[];
    	static int glob=0;
    	static int[] ans;
    	static boolean vis2[][];
    	//static long sum1=0;
    	//static long val[];
        static ArrayList<Integer> levels[];
        static int max=0;
        static int lev=1;
        static ArrayList<Integer> nodes[];
        static ArrayList<Integer> values[];
        static int depth[];
        static boolean found=false;
       // static long sm[];
        static int sum1=0;
        static int pre[][];
        static int subtree[];
       static  int cnt=0;
       static  HashMap<String,Integer> hm;
       static int sm[];
       static int size[];
       static long mul[];
       static long d[]=new long[1000000];
       static int tot=0;
       static long highest=(long)1e9;
       static boolean bit=false;
        static Stack<Integer> tt=new Stack();
       static HashSet<String> set=new HashSet<String>();
 	   static long fact[],num[];
 	   static long MOD=1000000007;
 	   static int value[];static int premen[];
 	   static int count=0,index=0;
 	   static double ans11[];
 	   static int price[];
 	   static ArrayList<String> hp[][];
 	   static boolean visit[][];
 	   static int cnu[]=new int[1000001];
 	   static int label=1;
 	   static int his[][];
 	   static int size1=0;
 	   static int up[],down[];
 	   static int TotalUp=0;
 	   static long dist[];
 	//   static HashMap<String,Integer> hm1=new HashMap();
 	  // static HashMap<Integer,Integer> hm2=new HashMap();
 	   static TreeSet<Long> set1=new TreeSet();
 	  static  long DP[][][]=new long[20][200][1500];
 	 	static int t=-1,n=-1;
 	 	static int two[],min[],r[];
 	 	static int total[];static int black[];
 	 	static int Parent[];
 	 	static int subtree1[][];
 	 	static char a[][];
 	 	static HashMap<String,TreeSet<Integer>> hm1;
 	 	static HashMap<String,TreeSet<Integer>> hm2;
 	 	static Stack<Integer> stack=new Stack();
 	 public static void solve() throws FileNotFoundException{
    		
    	
    		 in = new InputReader(System.in);
    		 pw = new PrintWriter(System.out);  
    	     int n=in.nextInt();
             int a[]=new int[n+1];
             int dp[]=new int[n+1];
             int fir[]=new int[5002];
             int las[]=new int[5002];
             Arrays.fill(fir,1000000);
             Arrays.fill(las,0);
             for(int i=1;i<=n;i++){
            	 a[i]=in.nextInt();
            	 fir[a[i]]=Math.min(fir[a[i]],i);
            	 las[a[i]]=Math.max(las[a[i]],i);
             }
             int xor[][]=new int[n+1][n+1];
             for(int i=1;i<=n;i++)
             {
            	 HashSet<Integer> set=new HashSet();
            	 int x=0;
            	 for(int j=i;j<=n;j++)
            	 {
            		 if(!set.contains(a[j]))
            		 {
            			 set.add(a[j]);
            			 x^=a[j];
            			 xor[i][j]=x;
            		 }
            		 else
            			 xor[i][j]=x;
            	 }
             }
             for(int i=1;i<=n;i++)
             {
            	 int min=Integer.MAX_VALUE;
            	 int max=0;
            	 for(int j=i;j>=1;j--)
            	 {
            		 min=Math.min(fir[a[j]],min);
            		 max=Math.max(max, las[a[j]]);
            		 if(min>=j&&max<=i)
            		 {
            			 dp[i]=Math.max(dp[i],dp[j-1]+xor[j][i]);
            		 }
            	 }
            	 dp[i]=Math.max(dp[i],dp[i-1]);
             }
             System.out.println(dp[n]);
 	 }
 	 public static void dfs2(int i,int j)
 	 {
 		 vis2[i][j]=true;
 		 
 		 if(i+1<2 && !vis2[i+1][j]&&a[i+1][j]=='#')
 		 {
 			 
 			 dfs2(i+1,j);
 		 }
 		 if(i-1>=0&&!vis2[i-1][j]&&a[i-1][j]=='#'){
 			 dfs2(i-1,j);
 		 }
 		 if(j+1<n&&!vis2[i][j+1]&&a[i][1+j]=='#'){
 			 
 			 dfs2(i,j+1);
 		 }
 		 if(j-1>=0&&!vis2[i][j-1]&&a[i][j-1]=='#'){
 			 dfs2(i,j-1);
 		 }
 	 }
 	 public static void topo(int curr)
 	 {
 		 visited[curr]=true;
 		 for(int x:g[curr])
 		 {
 			 if(!visited[x])
 				 topo(x);
 		 }
 		 stack.push(curr);
 	 }
 	 
 	 public static boolean IsPal(String s)
 	 {
 		 char c[]=s.toCharArray();
 		 for(int i=0;i<c.length/2;i++)
 		 {
 			 if(c[i]!=c[s.length()-1-i])
 				 return false;
 		 }
 		 return true;
 	 }
 	public static void Merge(long[] a,int p,int r){
        if(p<r){
            int q = (p+r)/2;
            Merge(a,p,q);
            Merge(a,q+1,r);
            Merge_Array(a,p,q,r);
        }
    }
    public static void Merge_Array(long a[],int p,int q,int r){
       long b[] = new long[q-p+1];
        long c[] = new long[r-q];
        for(int i=0;i<b.length;i++)
            b[i] = a[p+i];
        for(int i=0;i<c.length;i++)
            c[i] = a[q+i+1];
        int i = 0,j = 0;
        for(int k=p;k<=r;k++){
            if(i==b.length){
                a[k] = c[j];
                j++;
            }
            else if(j==c.length){
                a[k] = b[i];
                i++;
            }
            else if(b[i]<c[j]){
                a[k] = b[i];
                i++;
            }
            else{
                a[k] = c[j];
                j++;
            }
        }
    }
 	 
 	 
 	 public static void bfs(int i)
 	 {
 	    
 		 visited[i]=true;
 		 Queue<Integer> Q=new LinkedList();
 		 Q.add(i);
 		 while(!Q.isEmpty())
 		 {
 		 int curr=Q.poll();
 		 
 		 long right=r[curr];
 		 int cnt=0;
 		 int next=curr;
 		 while(cnt!=right)
 		 {
 			 cnt++;
 			 next++;
 			 if(next>=n)
 			 next%=n;
 			 if(!visited[next])
 			 {
 				 visited[next]=true;
 				 min[next]=Math.min(min[next],min[curr]+1);
 				 if(r[next]!=0)
 				 Q.add(next);
 			 }
 			 
 		 }
 		 cnt=0;
 		 long left=(r[curr]);
 		 next=curr;
 		 while(cnt!=left)
 		 {
 			 cnt++;
 			 next--;
 			 if(next<0)
 			 {
 				 next=next+n;
 			 }
 			 if(!visited[next])
 			 {
 				 visited[next]=true;
				 min[next]=Math.min(min[next],min[curr]+1);
				 if(r[next]!=0)
				 Q.add(next);
 			 }
 			 
 		 }
 		 }
 		
 	 }
 	
 	
       
 	  public static void dfs1(int curr,int parent)
 	  {
 		  visited[curr]=true;
 		  
 		  for(int x:g[curr])
 		  {
 			  
 			  if(x==parent)continue;
 			  depth[x]=depth[curr]+1;
 			  up[x]=up[curr];
 			  if(h[x].contains(curr)){
 				  up[x]++;
 				  TotalUp++;
 			  }
 			  dfs1(x,curr);
 		  }
 	  }
 	 
        
        
        public static void dfs(int curr,int Parent)
        {
        	visited[curr]=true;
        	size[curr]=1;
        	parent[curr]=Parent;
        	count++;
        	if(value[curr]>0)
        	{
        		index=value[curr];
        	}
        	for(int x:g[curr])
        	{
        		if(!visited[x])
        		{
        			dfs(x,curr);
        			size[curr]+=size[x];
        		}
        	}
        }
        static long ncr(long a, long b){
			if(b>a || b<0) return 0;
			long f = (fact[(int) a]*modInverse(((fact[(int) b]*fact[(int) (a-b)])%MOD), MOD))%MOD;
			return f;
		}
		static long modInverse(long a, long mOD2){
            return  power(a, mOD2-2, mOD2);
}
static 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;
}
 
        public static long gcd(long x, long y) {
    		if (x == 0)
    			return y;
    		else
    			return gcd( y % x,x);
    	}	
        public static long power(long a,long b)
		{
			long result=1;
			while(b>0)
			{
				if(b%2==1)
					result*=a;
				a=a*a;
				b/=2;
			}
			return result;
		}
        static class Pair implements Comparable<Pair>{
        	//int index;
        		int s;
        		int m;
        		//int index;
        		int h;
        		Pair(int index,int value,int y){
        	     	this.s=index;
        			this.m=value;
                    	this.h=y;
        		}
        		@Override
        		public int compareTo(Pair o) {
return 1;
        		}
        				
        	}
    	static class InputReader {
     
    		private InputStream stream;
    		private byte[] buf = new byte[8192];
    		private int curChar, snumChars;
    		private SpaceCharFilter filter;
     
    		public InputReader(InputStream stream) {
    			this.stream = stream;
    		}
     
    		public int snext() {
    			if (snumChars == -1)
    				throw new InputMismatchException();
    			if (curChar >= snumChars) {
    				curChar = 0;
    				try {
    					snumChars = stream.read(buf);
    				} catch (IOException e) {
    					throw new InputMismatchException();
    				}
    				if (snumChars <= 0)
    					return -1;
    			}
    			return buf[curChar++];
    		}
     
    		public   int nextInt() {
    			int c = snext();
    			while (isSpaceChar(c))
    				c = snext();
    			int sgn = 1;
    			if (c == '-') {
    				sgn = -1;
    				c = snext();
    			}
    			int res = 0;
    			do {
    				if (c < '0' || c > '9')
    					throw new InputMismatchException();
    				res *= 10;
    				res += c - '0';
    				c = snext();
    			} while (!isSpaceChar(c));
    			return res * sgn;
    		}
     
    		public long nextLong() {
    			int c = snext();
    			while (isSpaceChar(c))
    				c = snext();
    			int sgn = 1;
    			if (c == '-') {
    				sgn = -1;
    				c = snext();
    			}
    			long res = 0;
    			do {
    				if (c < '0' || c > '9')
    					throw new InputMismatchException();
    				res *= 10;
    				res += c - '0';
    				c = snext();
    			} while (!isSpaceChar(c));
    			return res * sgn;
    		}
     
    		public int[] nextIntArray(int n) {
    			int a[] = new int[n];
    			for (int i = 0; i < n; i++)
    				a[i] = nextInt();
    			return a;
    		}
     
    		public String readString() {
    			int c = snext();
    			while (isSpaceChar(c))
    				c = snext();
    			StringBuilder res = new StringBuilder();
    			do {
    				res.appendCodePoint(c);
    				c = snext();
    			} while (!isSpaceChar(c));
    			return res.toString();
    		}
     
    		public boolean isSpaceChar(int c) {
    			if (filter != null)
    				return filter.isSpaceChar(c);
    			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    		}
     
    		public interface SpaceCharFilter {
    			public boolean isSpaceChar(int ch);
    		}
    	}
    }
 