XOR

import java.io.*; // for handling input/output
import java.util.*; // contains Collections framework


class Main {  
    public static void main (String[] args) {
       Scanner sc=new Scanner(System.in);
       int n=sc.nextInt();
       int[] ar=new int[n];
       Map<Integer,Integer> m1=new HashMap<>();
       int xor=0;
      for(int i=0;i<n;i++)
      {
          ar[i]=sc.nextInt();
          if(m1.containsKey(ar[i]))
          {
             int count=m1.get(ar[i]);
             count=count+1;
             m1.put(ar[i],count);    
          }
          else
          {
            m1.put(ar[i],1);
          }
          
      }
     
     for(Map.Entry<Integer,Integer> m2:m1.entrySet())
     {
          if(m2.getValue()%2!=0)
          {
              xor=xor^m2.getKey();
          }
     }
     System.out.println(xor);
    
      
    }
}