#line 1 "/workspaces/compro/lib/template.hpp"


#line 1 "/workspaces/compro/lib/Assert/Assert.hpp"
#include <cassert>
#include <iostream>
#include <string>
#ifndef MY_ASSERT
#define MY_ASSERT

#ifdef LOCAL

#define ASSERT_MSG(expr, msg)                                                                                          \
  do {                                                                                                                 \
    if (!(expr)) {                                                                                                     \
      std::cerr << msg << std::endl;                                                                                   \
      assert(expr);                                                                                                    \
    }                                                                                                                  \
  } while (0)

#define FAIL ASSERT_MSG(false, "到達しない想定の場所に到達しました")

#else

#define ASSERT_MSG(...) (void)0
#define FAIL (void)0

#endif

#endif
#line 2 "/workspaces/compro/lib/io/vector.hpp"
#include <vector>

#ifndef IO_VECTOR
#define IO_VECTOR

template <class T> std::ostream &operator<<(std::ostream &out, const std::vector<T> &v) {
  int size = v.size();
  for (int i = 0; i < size; i++) {
    std::cout << v[i];
    if (i != size - 1)
      std::cout << " ";
  }
  return out;
}

template <class T> std::istream &operator>>(std::istream &in, std::vector<T> &v) {
  for (auto &el : v) {
    std::cin >> el;
  }
  return in;
}

#endif
#line 5 "/workspaces/compro/lib/template.hpp"
#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; i < (n); i++)
#define FOR(i, m, n) for (int i = (m); i < (n); i++)
#define RREP(i, n) for (int i = (n - 1); i >= 0; i--)
#define RFOR(i, m, n) for (int i = (n - 1); i >= (m); i--)
#define ALL(v) std::begin(v), std::end(v)
#define coutd(n) cout << fixed << setprecision(n)
#define ll long long int
#define vl vector<ll>
#define vi vector<int>
#define MM << " " <<

using namespace std;

struct P {
  ll x;
  ll y;
};

template <class T> void chmin(T &a, T b) {
  if (a > b)
    a = b;
}

template <class T> void chmax(T &a, T b) {
  if (a < b)
    a = b;
}

// 重複を消す。計算量はO(NlogN)
template <class T> void unique(std::vector<T> &v) {
  std::sort(v.begin(), v.end());
  v.erase(std::unique(v.begin(), v.end()), v.end());
}


#line 2 "main.cpp"

long long solve(int N, const std::vector<long long> &A) {
  int cnt = 0;
  REP(i, 63) {
    bool ok = [&](ll cand) -> bool {
      REP(j, N) {
        if ((A[j] & cand) != 0)
          return false;
      }
      return true;
    }(1LL << i);
    if (ok)
      return 1LL << i;
  }
  FAIL;
}

// generated by oj-template v4.8.1 (https://github.com/online-judge-tools/template-generator)
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int N;
  std::cin >> N;
  std::vector<long long> A(N);
  for (int i = 0; i < N; ++i) {
    std::cin >> A[i];
  }
  auto ans = solve(N, A);
  std::cout << ans << '\n';
  return 0;
}