package yukicoder;

import java.util.*;

public class Q130 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		long[] a = new long[n];
		for (int i = 0; i < n; ++i) {
			a[i] = sc.nextLong();
		}
		Arrays.sort(a);
		long ans = 0;
		for (int t = 0; t < 200; ++t) {
			for (long i = 32; i >= 0; --i) {// 3=1,1,
				if ((a[n - 1] & (1L << i)) > 0) {
					long[] tmp = Arrays.copyOf(a, n);
					long tmpMax = 0;
					for (int j = 0; j < n; ++j) {
						tmp[j] = a[j] ^ (1L << i);
						tmpMax = Math.max(tmpMax, tmp[j]);
					}
					if (tmpMax < a[n - 1]) {
						ans |= 1L << i;
						a = tmp;
						Arrays.sort(a);
						break;
					}
				}
			}
		}
		System.out.println(a[n - 1]);

	}
}