#include <bits/stdc++.h>
#define rep(i, l, r) for (int i = (l); i < (r); i++)
using namespace std;

typedef long long ll;

int main() {
    int N;
    cin >> N;
    vector<ll> A(N);
    rep(i, 0, N) cin >> A[i];
    rep(i, 0, 61) {
        ll ans = 1LL << i;
        rep(j, 0, N) {
            if (ans & A[j]) {
                ans = 0;
                break;
            }
        }
        if (ans) {
            cout << ans << endl;
            return 0;
        }
    }
}