#include "bits/stdc++.h"
#include<unordered_map>
#pragma warning(disable:4996)
using namespace std;
using ld = long double;
template<class T>
using Table = vector<vector<T>>;


vector<unsigned int>as;
int getans(const int keta, const vector<int>&nums) {
	if (keta < 0)return 0;
	vector<int>zeros;
	vector<int>ones;
	for (auto n : nums) {
		if (as[n]&(1 << keta)) {
			ones.push_back(n);
		}
		else {
			zeros.push_back(n);
		}
	}
	if (ones.empty()) {
		return getans(keta - 1, zeros);
	}
	else if (zeros.empty()) {
		return getans(keta - 1, ones);
	}
	else {
		return (1 << keta) + min(getans(keta - 1, zeros), getans(keta - 1, ones));
	}
}

int main() {
	int N; cin >> N;
	for (int i = 0; i < N; ++i) {
		int a; cin >> a;
		as.push_back(a);
	}
	vector<int>allnums(N);
	iota(allnums.begin(), allnums.end(), 0);
	
	int ans = getans(31,allnums);
	cout << ans << endl;
	return 0;
}