#include <bits/stdc++.h>
#include<iostream>
#include<map>
#include<vector>
#include <algorithm>
#include<math.h>
#include <iomanip>
#include<set>
#include <numeric>
#include<string>
using ll = long long;
using namespace std;

int main()
{
    ll n, ans = 1;
    cin >> n;
    vector<ll> a(n);
    for (int i = 0; i < n; i++) cin >> a[i];
    while (ans){
        for (int i = 0; i < n; i++){
            if ((a[i] & ans)) break;
            if (i == n-1 && !(a[i] & ans)){
                cout << ans << endl;
                return 0;
            }
        }
        ans <<= 1;
    }
}