// yukicoder: No.130 XOR Minimax
// 2019.8.7 bal4u

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

#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

int in() {   // 非負整数の入力
	int n = 0, c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	return n;
}

int a[100005];

int calc(int sz, int *a, int b) {
	int *u, *v, wu, wv, i, ans;
	if (b < 0 || sz == 1) return 0;
	if (sz == 2) {
		return ((a[0] >> b) ^ (a[1] >> b))? 1<<b: 0;
	}
	u = malloc(sizeof(int)*sz), v = malloc(sizeof(int)*sz);
	wu = wv = 0;
	for (i = 0; i < sz; i++) {
		if ((a[i] >> b) & 1) u[wu++] = a[i]; else v[wv++] = a[i];
	}
	if (wu == 0 || wv == 0) {
//		free(u), free(v);
		ans = calc(sz, a, b-1);
	} else {
		ans = calc(wu, u, b-1);
		int t = calc(wv, v, b-1);
		if (t < ans) ans = t;
		ans |= 1<<b;
//		free(u), free(v);
	}
	return ans;
}
	
int main()
{
	int i, N, ma;

	N = in();
	if (N == 1) { puts("0"); return 0; }
	ma = 0;	for (i = 0; i < N; i++) {
		a[i] = in();
		if (a[i] > ma) ma = a[i];
	}
	i = -1; while (ma) ma >>= 1, i++;
	printf("%d\n", calc(N, a, i));
	return 0;
}