#include <iostream>
#include <vector>
#include <string>
#include <utility>
#include <algorithm>
#include <climits>
#include <map>
#include <queue>
#include <cmath>
#include <set>
#include <stdexcept>

using namespace std;

using int64 = long long;


int main() {
    int n;
    cin >> n; cin.ignore();
    vector<string> a(n);
    for (int i=0; i<n; i++) {
        getline(cin, a[i]);
        try{ stoll(a[i]); }
        catch (const logic_error& e) {
            cout << "\"assert\"" << endl;
            return 0;
        }
    }

    set<int64> s;
    for (int i=0; i<n; i++) {
        for (int j=i+1; j<n; j++) {
            s.insert(stoll(a[i]) + stoll(a[j]));
        }
    }

    cout << *++s.rbegin() << endl;
}