#include <bits/stdc++.h>
using namespace std::literals::string_literals;
using i64 = std::int_fast64_t;
using std::cout;
using std::endl;
using std::cin;

template<typename T>
std::vector<T> make_v(size_t a){return std::vector<T>(a);}

template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts){
  return std::vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}

std::pair<int, int> solve(int k, const std::vector<int>& now) {
	if(k < 0 or now.empty()) return {-(1 << k + 1), 0};
	
	std::vector<int> X, Y;
	for(auto v: now) {
		if(v >> k & 1) X.push_back(v);
		else Y.push_back(v);
	}
	
	auto [x, p] = solve(k - 1, X);
	auto [y, q] = solve(k - 1, Y);
	if(x < y) return {x + (1 << k) | (1 << k), p};
	return {y + (1 << k), q | (1 << k)};
}

int main() {
	int n; scanf("%d", &n); std::vector<int> a(n);
	for(int i = 0; i < n; i++) scanf("%d", &a[i]);
	
	printf("%d\n", solve(30, a).first);
	return 0;
}