#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
using namespace std;

struct Trie {
	Trie *next[2];

	Trie() {
		fill(next, next + 2, (Trie *)0);
	}

	void insert(const char *s) {
		if (*s == '\0') return;
		if (this->next[*s-'0'] == NULL)
			this->next[*s-'0'] = new Trie();
		this->next[*s-'0']->insert(s + 1);
	}

	bool find(const char *s) {
		if (*s == '\0') return true;
		if (this->next[*s-'0'] == NULL)
			return false;
		return this->next[*s-'0']->find(s + 1);
	}
};

string binary(int a, int l = 32) {
	string s = "";
	for (int i = 0; i < l; i++) {
		s += to_string(a & 1);
		a >>= 1;
	}
	reverse(s.begin(), s.end());
	return s;
}
int binary_to_int(string bi) {
	int a = 0;
	for (int i = 0; i < bi.size(); i++) {
		a += (bi[bi.size() - 1 - i] - '0') << i;
	}
	return a;
}

string solve(Trie* trie) {
	bool exist0 = trie->find("0"), exist1 = trie->find("1");
	string bi = "";

	if (exist0 && !exist1)bi = "0" + solve(trie->next[0]);
	else if(!exist0 && exist1)bi = "0" + solve(trie->next[1]);
	else if (!exist0 && !exist1)return bi;
	else {
		string next_bi0 = "1" + solve(trie->next[0]);
		string next_bi1 = "1" + solve(trie->next[1]);
		if (binary_to_int(next_bi0) < binary_to_int(next_bi1))bi = next_bi0;
		else bi = next_bi1;
	}

	return bi;
}



int main()
{
	int n; cin >> n;
	vector<string>binaryA(n);
	for (int i = 0; i < n; i++) {
		int a; cin >> a;
		binaryA[i] = binary(a);
	}

	Trie* trie = new Trie();
	for (int i = 0; i < n; i++) {
		trie->insert(binaryA[i].data());
	}

	cout << binary_to_int(solve(trie)) << endl;

	return 0;
}