#include <bits/stdc++.h>

using namespace std;

int solve(int d, vector<int>& v) {
	if (v.size() <= 1) return 0;
	vector<int> w[2];
	for (int x : v) {
		w[(x >> d) & 1].push_back(x);
	}
	if (w[0].empty()) return solve(d - 1, w[1]);
	if (w[1].empty()) return solve(d - 1, w[0]);
	int res = (1 << d);
	res += min(solve(d - 1, w[0]), solve(d - 1, w[1]));
	return res;
}

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int n;
	cin >> n;
	vector<int> a(n);
	for (int i = 0; i < n; i++) cin >> a[i];
	sort(a.begin(), a.end());
	a.erase(unique(a.begin(), a.end()), a.end());
	cout << solve(29, a) << endl;
	return 0;
}