784_C. INTERCALC_18747
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.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class Main {

    public static void main(String[] args) throws IOException {
        FastScanner in = new FastScanner(System.in);
        int n = in.nextInt();
        int t[] = new int[n];
        int max = 0;
        for (int i = 0; i < t.length; i++) {
            t[i] = in.nextInt();
            max = Math.max(max, t[i]);
        }
        System.out.println((max^t[n-1]));
        
    }

    static class FastScanner {

        private BufferedReader in;
        private String[] line;
        private int index;
        private int size;

        public FastScanner(InputStream in) throws IOException {
            this.in = new BufferedReader(new InputStreamReader(in));
            init();
        }

        public FastScanner(String file) throws FileNotFoundException {
            this.in = new BufferedReader(new FileReader(file));
        }

        private void init() throws IOException {
            line = in.readLine().split(" ");
            index = 0;
            size = line.length;
        }

        public int nextInt() throws IOException {
            if (index == size) {
                init();
            }
            return Integer.parseInt(line[index++]);
        }

        public long nextLong() throws IOException {
            if (index == size) {
                init();
            }
            return Long.parseLong(line[index++]);
        }

        public float nextFloat() throws IOException {
            if (index == size) {
                init();
            }
            return Float.parseFloat(line[index++]);
        }

        public double nextDouble() throws IOException {
            if (index == size) {
                init();
            }
            return Double.parseDouble(line[index++]);
        }

        public String next() throws IOException {
            if (index == size) {
                init();
            }
            return line[index++];
        }

        public String nextLine() throws IOException {
            if (index == size) {
                init();
            }
            StringBuilder sb = new StringBuilder();
            for (int i = index; i < size; i++) {
                sb.append(line[i]).append(" ");
            }
            return sb.toString();
        }

        private int[] nextIntArray(int n) throws IOException {
            int[] tab = new int[n];
            for (int i = 0; i < tab.length; i++) {
                tab[i] = nextInt();
            }
            return tab;
        }

    }
}
