#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define rep1(i, n) for (ll i = 1; i <= n; ++i)
#define reps(i, s, e) for (ll i = s; i <= e; ++i)
using ll = long long;
using ld = long double;
using cp = complex<ld>;
using pa = pair<ll, ll>;
using tup = tuple<ll, ll, ll>;
using vp = vector<pair<ll, ll>>;
using vtup = vector<tuple<ll, ll, ll>>;
using st = string;
using vs = vector<string>;
using vc = vector<char>;
using vvi = vector<vector<ll>>;
using vvc = vector<vector<char>>;
using vi = vector<ll>;
const ll MOD1 = 1000000007;
const ll MOD2 = 998244353;
const ll INF = (1LL << 60);

int main() {
  ll n;
  cin >> n;
  vi a(n);
  rep(i, n) cin >> a[i];

  for (int i = 0;; i++) {
    ll t = 1LL << i;
    bool valid = true;
    rep(j, n) {
      if (a[j] & t) {
        valid = false;
        break;
      }
    }
    if (valid) {
      cout << t << endl;
      break;
    }
  }
}