// yukicoder: No.130 XOR Minimax
// 2019.4.11 bal4u

#include <stdio.h>
#include <stdlib.h>

#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif
int in()
{
	int n = 0, c = gc();
	do n = 10 * n + (c & 0xf), c = gc(); while (c >= '0');
	return n;
}

int a[100005];

int main()
{
	int i, N, x, t, ans;

	x = (1 << 30) - 1, N = in();
	for (i = 0; i < N; i++) x &= a[i] = in();
	ans = 0;
	for (i = 0; i < N; i++) {
		if ((t = x ^ a[i]) > ans) ans = t;
	}
	printf("%d\n", ans);
	return 0;
}