int n;
    cin >> n;
    vector<ll> v(n);
    map<ll, bool> m;
    for (auto &i : v)
    {
        cin >> i;
        m[i] = true;
    }
    for (int i = 0; i <= 2000; i++)
    {
        if (!m[i])
        {
            cout << i << endl;
            return;
        }
    }