#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;

int N;
int a[100010];

int main() {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  
  cin >> N;
  for (int i = 0; i < N; i++) {
    cin >> a[i];
  }
  sort(a, a+N);
  int d = 0, ans = 0;
  while (!(a[N-1] < (1 << d))) {
    int bit[2] = {};
    for (int i = 0; i < N; i++) {
      bit[(a[i] >> d & 1)]++;
    }
    if (bit[0] != 0 && bit[1] != 0) ans += (1 << d);
    d++;
  }
  cout << ans << endl;

  return 0;
}