import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.PriorityQueue;
public class Main {
	public static void main(String[] args) throws NumberFormatException, IOException{
		ContestScanner in = new ContestScanner();
		int n = in.nextInt();
		long[] a = new long[n];
//		PriorityQueue<Long> qu = new PriorityQueue<Long>();
		long and = 0xffffffff;
		long or = 0;
		for(int i=0; i<n; i++){
			a[i] = in.nextLong();
			and &= a[i];
			or |= a[i];
//			qu.add(a[i]);
		}
		if(or == 0){
			System.out.println(0);
			return;
		}
		long xor = 0;
		long tmp = or;
		int j=0;
		while(tmp > 0){
			tmp >>= 1;
			j++;
		}
		j--;
		tmp = 0xffffffff;
		while(j >= 0){
			tmp <<= 1;
			j--;
		}
//		System.err.println(~tmp);
		xor |= and;
		xor &= ~or & ~tmp;
		long max = 0;
		for(int i=0; i<n; i++){
			long res = a[i] ^ xor;
			if(res > max) max = res;
		}
		System.out.println(max);
//		while(!qu.isEmpty()){
//			long val = qu.poll();
//			long next = qu.peek();
//			
//		}
	}
}

class MyComp implements Comparator<int[]>{
	public int compare(int[] a, int[] b) {
		return a[0] - b[0];
	}
}
//
//class Reverse implements Comparator<Integer>{
//	public int compare(Integer arg0, Integer arg1) {
//		return arg1 - arg0;
//	}
//}

class Node implements Comparable<Node>{
	int id;
	int qNum;
	int xor;
	List<Node> edge = new ArrayList<Node>();
	public Node(int id, int q, int xor){
		this.id = id;
		qNum = q;
		this.xor = xor;
	}
	public void createEdge(Node node){
		edge.add(node);
	}
	
	@Override
	public int compareTo(Node n) {
		return n.qNum - qNum;
	}
}


class MyMath{
	public final static double PIhalf = Math.PI/2.0;
	public static double pAngle(double x, double y){
		// ベクトル(1, 0)と(x, y)とのなす角を返す(rad:0 to 2pi)
		if(x == 0){
			if(y == 0){
				System.err.println("pAngle error: zero vector.");
				return 0;
			}else if(y < 0){
				return PIhalf*3.0;
			}else{
				return PIhalf;
			}
		}
		double rad = Math.atan(y/x);
		if(rad < 0){
			rad += Math.PI*2.0;
		}
		return rad;
	}
	public static long fact(long n){
		long res = 1;
		while(n > 0){
			res *= n--;
		}
		return res;
	}
	public static long[][] pascalT(int n){
		long[][] tri = new long[n][];
		for(int i=0; i<n; i++){
			tri[i] = new long[i+1];
			for(int j=0; j<i+1; j++){
				if(j == 0 || j == i){
					tri[i][j] = 1;
				}else{
					tri[i][j] = tri[i-1][j-1] + tri[i-1][j];
				}
			}
		}
		return tri;
	}

	// 最大公約数
	static int gcd(int a, int b){
		return b == 0 ? a : gcd(b, a % b);
	}

	// 最小公倍数
	static int lcm(int a, int b){
		return a * b / gcd(a, b);
	}
}

class ContestScanner{
	private BufferedReader reader;
	private String[] line;
	private int idx;
	public ContestScanner() throws FileNotFoundException{
		reader = new BufferedReader(new InputStreamReader(System.in));
	}

	public ContestScanner(String filename) throws FileNotFoundException{
		reader = new BufferedReader(new InputStreamReader(new FileInputStream(filename)));
	}
	
	public String nextToken() throws IOException{
		if(line == null || line.length <= idx){
			line = reader.readLine().trim().split(" ");
			idx = 0;
		}
		return line[idx++];
	}
	public long nextLong() throws IOException, NumberFormatException{
		return Long.parseLong(nextToken());
	}
	public int nextInt() throws NumberFormatException, IOException{
		return (int)nextLong();
	}
	public double nextDouble() throws NumberFormatException, IOException{
		return Double.parseDouble(nextToken());
	}
}