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.Scanner;

public class Test
{
	public static int max(int a[])
	{
		int max = a[0];
		for(int i = 1; i < a.length; i++)
			if(a[i] > max)
				max = a[i];
		
		return max;
	}
	
	public static void main(String[] args)
	{
		Scanner in = new Scanner(System.in);
		
		int n = in.nextInt();
		int a[] = new int[n];
		for(int i = 0; i < a.length; i++)
			a[i] = in.nextInt();
		
		in.close();
		
		int maxx = max(a);
		
		System.out.println(maxx ^ a[a.length - 1]);
	}

}
