#include <bits/stdc++.h>
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")

#define int long long
#define ld long double
#define vec vector
#define all(m) (m).begin(), (m).end()
#define forn(i,n) for(int i=0;i<(n);i++)

// TIP To <b>Run</b> code, press <shortcut actionId="Run"/> or click the <icon src="AllIcons.Actions.Execute"/> icon in the gutter.
using namespace std;

void solve() {
    int n;
    cin >> n;
    vec<int> a(n);
    forn(i,n) cin >> a[i];
    int ans = 0;
    int mask = 1;
    int bit = 1;
    int mxx = 1e18;
    while (bit<=mxx) {
        bool flag = false;
        forn(i,n) {
            if (bit&a[i]) {
                ans += bit;
                flag = true;
                break;
            }
        }
        if (!flag) {
            int sm = 0;
            forn(i,n) {
                sm += a[i]&mask;
                if (sm>=bit) {
                    ans += bit;
                    break;
                }
            }
        }
        bit <<= 1;
        mask<<=1;
        mask++;
    }
    cout<<ans<<'\n';
}

signed main() {

    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    int tt = 1;
    // cin>>tt;
    while (tt--)
        solve();
    return 0;
}