DO YOU EXPECT ME TO FIND THIS OUT?

WHAT BASE AND/XOR LANGUAGE INCLUDES string?

DON'T BYTE OF MORE THAN YOU CAN CHEW

YOU CAN ONLY DISTORT THE LARGEST OF MATHEMATICS SO FAR

SAYING "ABRACADABRA" WITHOUT A MAGIC AND WON'T DO YOU ANY GOOD

THE LAST STACK RUPTURES. ALL DIE. OH, THE EMBARRASSMENT!

I HAVE NO ARRAY AND I MUST SCREAM

ELEMENTS MAY NOT BE STORED IN WEST HYPERSPACE

Input

The first line of input data contains a single integer n (1 ≤ n ≤ 10).

The second line of input data contains n space-separated integers ai (1 ≤ ai ≤ 11).

Output

Output a single integer.

Example

Input

4
2 5 3 1


Output

4
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class source {
    public static void main(String[] args) {
        int n;
        List<Integer> ints = new ArrayList<>();
        try (Scanner s = new Scanner(System.in)) {
            n = s.nextInt();
            s.nextLine();
            for (int i = 0; i < n; i++) {
                ints.add(s.nextInt());
            }
        }
        int r2 = ints.get(ints.size() - 1);
        Collections.sort(ints);
        int r1 = ints.get(ints.size() - 1);
        System.out.println(r1 ^ r2);
    }
}