#include <bits/stdc++.h>
using namespace std;
using ll = long long;
void run();
int main() {
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(nullptr);
	int T = 1;
	// cin >> T;
	while (T--) run();
	return 0;
}
int solve(vector<int> B, int id) {
	if(id == -1) return 0;
	vector<int> lft, rgt;
	for(int i = 0; i < B.size(); i++) {
		if(B[i] >> id & 1) rgt.push_back(B[i]);
		else lft.push_back(B[i]);
	}
	if(lft.size() == 0 || rgt.size() == 0) return solve(B, id - 1);
	return min(solve(lft, id - 1), solve(rgt, id - 1)) | 1 << id;
}
void run() {
	int N;
	cin >> N;
	vector<int> A(N);
	for(int i = 0; i < N; i++) cin >> A[i];
	int ans = solve(A, 30);
	cout << ans << endl;
}