//效率不通過
public class Main {
static int N ;
static int[] arr ;
static HashSet<Integer> set = new HashSet<Integer>();
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
N = sc.nextInt();
arr = new int[N];
for (int i = 0; i < N; i++) {
arr[i] = sc.nextInt();
}
Arrays.sort(arr);
for (int i = 0; i < N; i++) {
if (set.contains(arr[i])) {
set.remove(arr[i]);
}else {
set.add(arr[i]);
}
}
for(Object o : set) {
System.out.println(o);
}
sc.close();
}
}
public class Main {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
int n = s.nextInt();
int res = 0;
for (int i = 0; i < n; i++) {
res = res ^ s.nextInt();
}
System.out.println(res);
s.close();
}}
public class Main{
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
int a[]=new int[10000001];
int num;
int n=sc.nextInt();
for (int i = 0; i < n; i++) {
num=sc.nextInt();
a[num]++;
}
for (int i = 0; i < 10000001; i++) {
if(a[i]%2==1){
System.out.println(i);
break;
}
}
sc.close();
}
}
