#include <bits/stdc++.h>
using namespace std;
const int OO = 1e9;
const double EPS = 1e-9;
template <class T>
void _db(const char* dbStr, T e) {
  cout << dbStr << " = " << e << endl;
}
template <class T, class... L>
void _db(const char* dbStr, T e, L... r) {
  while (*dbStr != ',') cout << *dbStr++;
  cout << " = " << e << ',';
  _db(dbStr + 1, r...);
}
template <class S, class T>
ostream& operator<<(ostream& o, const map<S, T>& v) {
  o << "[";
  int i = 0;
  for (const pair<S, T>& pr : v)
    o << (!i++ ? "" : ", ") << "{" << pr.first << " : " << pr.second << "}";
  return o << "]";
}
template <template <class, class...> class S, class T, class... L>
ostream& operator<<(ostream& o, const S<T, L...>& v) {
  o << "[";
  int i = 0;
  for (const auto& e : v) o << (!i++ ? "" : ", ") << e;
  return o << "]";
}
template <class S, class T>
ostream& operator<<(ostream& o, const pair<S, T>& pr) {
  return o << "(" << pr.first << ", " << pr.second << ")";
}
ostream& operator<<(ostream& o, const string& s) {
  for (const char& c : s) o << c;
  return o;
}
template <class T>
using V = vector<T>;
template <class T>
using VV = V<V<T>>;
template <class T>
using VVV = VV<V<T>>;
using ll = long long;
using pii = pair<int, int>;
using vi = V<int>;
using vii = V<pii>;
using vvi = VV<int>;
using mii = map<int, int>;
using umii = unordered_map<int, int>;
using si = set<int>;
using usi = unordered_set<int>;
int LOG(int x) {
  int ret = 0;
  while (x) ++ret, x >>= 1;
  return ret;
}
int n;
mii pref, mem;
int dp(int i) {
  if (LOG(i) == 31) return 0;
  if (!(pref.find(i << 1) != pref.end())) return dp((i << 1) + 1);
  if (!(pref.find((i << 1) + 1) != pref.end())) return dp(i << 1);
  if ((mem.find(i) != mem.end())) return mem[i];
  return mem[i] = (1 << (30 - LOG(i))) + min(dp(i << 1), dp((i << 1) + 1));
}
int main() {
  ios::sync_with_stdio(false);
  cout.precision(10);
  cin.tie(0);
  int x = (1LL << 31) - 1;
  true;
  cin >> n;
  int a;
  for (int i = 0; i < n; ++i) {
    cin >> a;
    a |= (1 << 30);
    while (a) ++pref[a], a >>= 1;
  }
  true;
  cout << dp(1) << '\n';
  return 0;
}
