#include <iostream>
#include <algorithm>
#define int long long
using namespace std;

int n;
int a[100000];

//[l, r)
int dfs(int l, int r, int ind) {
	if (ind < 0) return 0;
	
	int i;
	for (i = l; i < r; i++) if ((a[i] >> ind) % 2) break;
	if (i == l || i == r) return dfs(l, r, ind - 1);
	return (1LL << ind) + min(dfs(l, i, ind - 1), dfs(i, r, ind - 1));
}

signed main() {
	cin >> n;
	for (int i = 0; i < n; i++) cin >> a[i];
	cout << dfs(0, n, 35) << endl;
	return 0;
}