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

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 flag = true;
    for (int j = 0; j < N; j++) {
      if (t & A[j]) {
        flag = false;
        break;
      }
    }
    if (flag) {
      cout << t << endl;
      return 0;
    }
  }
  return 0;
}