#include <iostream>
#include <algorithm>
#include <vector>
#include <string>

using lint = long long;

void solve() {
    int n;
    std::cin >> n;

    {
        std::string tmp;
        std::getline(std::cin, tmp);
    }

    std::vector<lint> xs(n);
    for (auto& x : xs) {
        std::string s;
        std::getline(std::cin, s);

        if (std::count(s.begin(), s.end(), ' ')) {
            std::cout << "\"assert\"" << std::endl;
            return;
        }

        x = std::stoll(s);
    }

    std::vector<lint> ss;
    for (int j = 0; j < n; ++j) {
        for (int i = 0; i < j; ++i) {
            ss.push_back(xs[i] + xs[j]);
        }
    }

    std::sort(ss.rbegin(), ss.rend());
    ss.erase(std::unique(ss.begin(), ss.end()), ss.end());
    std::cout << ss[1] << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}