#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll a[62];
bool flag[62];
void init()
{
  a[0] = 1;
  for (int i = 1; i < 63; i ++)
  {
    a[i] = a[i - 1] * 2; 
  }
}
int main()
{
  init();
  int N; cin >> N;
  vector<ll> A(N);
  for (int i = 0; i < N; i ++) cin >> A[i];
  
  for (int i = 0; i < 63; i ++)
  {
    for (int j = 0; j < N; j ++)
    {
      if ((A[j] & a[i]) != (A[j] + a[i])) {flag[i] = false; break;}
      else flag[i] = true;
    }
    if (flag[i]) break;
  }
  for (int i = 0; i < 63; i ++)
  {
    if (flag[i]) 
    {
      cout << a[i] << "\n";
      break;
    }
  }
  return 0;
}