#include <bits/stdc++.h>

using namespace std;

long long dfs(vector<long long> a, int d = 1<<30) {
  vector<long long> b, c;
  for (long long x: a) {
    if (x & d)
      b.push_back(x ^ d);
    else
      c.push_back(x);
  }

  if (d == 1) return (b.size() && c.size()) ? 1 : 0;
  if (!c.size()) return dfs(b, d>>1);
  if (!b.size()) return dfs(c, d>>1);
  
  long long ret = min(dfs(b, d>>1), dfs(c, d>>1));
  return d | ret;
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n;
  cin >> n;
  vector<long long> a(n);
  for (int i = 0; i < n; i++)
    cin >> a[i];

  cout << dfs(a) << endl;
  
  return 0;
}