S_N7

#include <iostream>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
#include <string>
#include <stack>
#include <set>
#include <map>
#define pii pair <int, int>
#define pb(x) push_back(x)
using namespace std;
using ll = long long;
using ld = long double;
using db = double;
void cv(vector <int> &v) {
    for (auto x : v) cout << x << ' ';
    cout << "\n";
}

void cvl(vector <ll> &v) {
    for (auto x : v) cout << x << ' ';
    cout << "\n";
}


void cvv(vector <vector <int> > &v) {
    for (auto x : v) cv(x);
    cout << "\n";
}

void cvb(vector <bool> v) {
    for (bool x : v) cout << x << ' ';
    cout << "\n";
}

void cvs(vector <string>  v) {
    for (auto a : v) {
        cout << a << "\n";
    }
}

void cvp(vector <pii> a) {
    for (auto p : a) {
        cout << p.first << ' ' << p.second << "\n";
    }
    cout << "\n";
}

#include <fstream>

void f(vector <pii> &ar) {
    sort(ar.begin(), ar.end());
    reverse(ar.begin(), ar.end());
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    string data;
    ifstream file("sum27-A_2.txt");
    //ifstream file("test.txt");
    getline(file, data);
    int n = stoi(data);
    vector <pii> ar, A, B, C;
    for (int i = 0; i < n; ++i) {
        getline(file, data);
        int x = stoi(data);
        ar.push_back({x,i});
        if (x % 14 == 0) {
            C.push_back({x,i});
        } else if (x % 7 == 0) {
            B.push_back({x,i});
        } else if (x % 2 == 0) {
            A.push_back({x,i});
        }
    }
    f(ar);
    f(A);
    f(B);
    f(C);
    int ans = -1;
    if (!A.empty() && !B.empty()) {
        ans = A[0].first * B[0].first;
    }
    int i = 0;
    if (!C.empty() && C[0] == ar[i]) {
        i++;
    }
    if (!C.empty()) {
        ans = max(ans, C[0].first * ar[i].first);
    }
    cout << ans;
}