import java.io.BufferedInputStream;
import java.io.IOException;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.*;
import java.util.Map.Entry;

public class Main {
	public static final int C =  1000000007;
	static final int CY = 1000000000;
	//static boolean MAP[][];
	static int N;
	static long M;
	static int MAX = -1;
	//static int tic[][];
	static int A[];
	//static int max;
	static int DP[][][];
	static int ST[][];
	//static int p[];
	//static ArrayList<HashSet<Integer>> al;
	static TreeMap<Integer, ArrayList<Integer>> hm;
	//static ArrayList<Integer> al;
	//static int a[][];
	//static char[][] ch;
	//static ArrayList<HashMap<Long, Long>> al;
	//static String a[];
	//static String str;

	public static void main(String[] args) {
		//StringBuilder sb = new StringBuilder();
		BufferedInputStream bs = new BufferedInputStream(System.in);
		Scanner sc = new Scanner(bs);
		
		N = sc.nextInt();
		
		A= new int[N];
		for (int i=0; i < N; i++) {
			A[i] = Integer.parseInt(sc.next());
			
		}
		
		

		
		//BigInteger bi = new BigInteger("0");
		
		long ans = Integer.MAX_VALUE;
		
		for (int i=0; i < N; i++){
			int max = 0;
			for (int t=0; t < N; t++) {
				max = Math.max(max, A[i] ^ A[t]);
				
			}
			ans = Math.min(ans, max);
		}
		
		
		System.out.println(ans);


	}
	

	

}