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.Scanner;

public class INTERCALC {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner in = new Scanner(System.in);
		
		int n = in.nextInt();
		ArrayList<Integer> all = new ArrayList<Integer>();
		for (int i = 0; i < n; i++) {
			all.add(in.nextInt());
		}
		
		int max = 0-Integer.MAX_VALUE;
		for (int i = 0; i < all.size(); i++) {
			if (all.get(i) > max) {
				max=all.get(i);
			}
		}
		System.out.println(max ^ all.get(all.size()-1));
	}

}