#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n - 1); i >= 0; i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) int(x.size())
using namespace std;
using ll = long long;
const int INF = 1e9;
const ll LINF = 1e18;
template <class T>
bool chmax(T& a, const T& b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T& a, const T& b) {
    if (b < a) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
vector<T> make_vec(size_t a) {
    return vector<T>(a);
}
template <class T, class... Ts>
auto make_vec(size_t a, Ts... ts) {
    return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));
}
template <typename T>
istream& operator>>(istream& is, vector<T>& v) {
    for (int i = 0; i < int(v.size()); i++) {
        is >> v[i];
    }
    return is;
}
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    for (int i = 0; i < int(v.size()); i++) {
        os << v[i];
        if (i < int(v.size()) - 1) os << ' ';
    }
    return os;
}
int main() {
    int n;
    cin >> n;
    vector<int> cnt(200200);
    rep(i, n) {
        int a;
        cin >> a;
        cnt[a]++;
    }

    int ok = 0, ng = n, mid;
    while (ng - ok > 1) {
        // 0以上mid未満を2枚ずつ揃えられるか
        mid = (ok + ng) / 2;
        int x = 0, y = 0;
        rep(i, 200200) {
            if (i < mid) {
                if (cnt[i] < 2) x += 2 - cnt[i];
                if (cnt[i] > 2) y += cnt[i] - 2;
            } else {
                y += cnt[i];
            }
        }
        (x <= 1 && y >= x ? ok : ng) = mid;
    }
    cout << ok << '\n';
}