#include "bits/stdc++.h"
using namespace std;
#ifdef _DEBUG
#include "dump.hpp"
#else
#define dump(...)
#endif

//#define int long long
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(b)-1;i>=(a);i--)
#define all(c) begin(c),end(c)
const int INF = sizeof(int) == sizeof(long long) ? 0x3f3f3f3f3f3f3f3fLL : 0x3f3f3f3f;
const int MOD = 1'000'000'007;
template<class T> bool chmax(T &a, const T &b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, const T &b) { if (b < a) { a = b; return true; } return false; }

int f(int k, vector<int> &v) {
	dump(k, v);
	if (v.size() == 1)return 0;
	vector<int> w[2];
	for (auto x : v) {
		w[x >> k & 1].push_back(x);
	}
	if (w[0].size() == 0)
		return f(k - 1, w[1]);
	if (w[1].size() == 0)
		return f(k - 1, w[0]);
	return 1 << k + min(f(k - 1, w[1]), f(k - 1, w[0]));
}

signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N; cin >> N;
	vector<int> a(N); rep(i, 0, N) {
		cin >> a[i];
	}
	sort(all(a));
	a.erase(unique(a.begin(), a.end()), a.end());
	cout << f(30, a) << endl;
	return 0;
}