#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define N 500017
#define ll long long
using namespace std;
int n;ll a[N];
int main()
{
	cin >> n;
	for(int i = 1;i <= n;i += 1)cin >> a[i];
	sort(a+1,a+n+1);
	ll minn = a[1]|a[2];
	for(int i = 1;i < n;i += 1)minn = min(minn,a[i]^a[i+1]);
	cout << minn << endl;
	return 0;
}