#include "bits/stdc++.h"
using namespace std;

int dfs(vector<int> T, int p){
	if (p < 0) return 0;
	vector<int> A;
	vector<int> B;
	for (auto num : T){
		if ((num >> p) % 2 == 0) A.push_back(num);
		else B.push_back(num);
	}
	int ans = 0;
	if (A.size() == 0 || B.size() == 0) ans = dfs(T, p - 1);
	else{
		ans = dfs(A, p - 1);
		ans = min(ans, dfs(B, p - 1));
		ans += 1 << p;
	}
	return ans;
}

int main() {
	int N;
	cin >> N;
	vector<int> A(N);
	for (int i = 0; i < N; i++)
	{
		cin >> A[i];
	}
	cout << dfs(A, 30) << endl;
}