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

int main() {
  int n;
  cin >> n;
  vector<ll> a(n);
  for (int i = 0; i < n; i++) cin >> a[i];
  for (int i = 0;; i++) {
    ll t = 1LL << i;
    bool valid = true;
    for (int j = 0; j < n; j++) {
      if (a[j] & t) {
        valid = false;
        break;
      }
    }
    if (valid) {
      cout << t << "\n";
      break;
    }
  }
}