#include <algorithm>
#include <array>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <numeric>
#include <optional>
#include <queue>
#include <set>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

int main() {
    int32_t n;
    cin >> n;
    vector<int32_t> as(2 * n);
    for (auto &&a : as) {
        cin >> a;
    }
    sort(as.begin(), as.end());
    int64_t ans = 0;
    for (auto i = 0; i < n; ++i) {
        ans += int64_t(as[i * 2]) * as[i * 2 + 1];
    }
    cout << ans << endl;
    return 0;
}