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.*;
public class NumbersJoke {

	public static void main(String[] args) {
		// TODO Aut	o-generated method stub
		Scanner in =  new Scanner(System.in) ;
		int n  = in.nextInt()  ; 
		int a [] = new int[n] ; 
		for(int i = 0 ; i<n  ; i++){
			a[i] = in.nextInt()  ; 
		}
		int last = a[a.length -1] ; 
		int max = 0 ; 
		Arrays.sort(a);
		max = a[a.length -1] ;
		System.out.println(last ^ max);
	}
}
