#include <iostream>
#include <algorithm>
#include <vector>
#include <set>

typedef long long ll;

struct Pair {
    int x, y;
};

int main() {
    freopen("input.txt", "rt", stdin);

    //std::ios_base_sync_with_stdio(false);
    //std::cin.tie(0); std::cout.tie(0); std::cerr.tie(0);

    int n, limit; std::cin >> n >> limit;

    auto cmpx = [](const Pair& a, const Pair& b){
        return a.x < b.x || (a.x == b.x && a.y < b.y);
    };

    auto cmpy = [](const Pair& a, const Pair& b){
        return a.y < b.y || (a.y == b.y && a.x < b.x);
    };

    std::vector<Pair> ordered_x, ordered_y;
    for (int i = 0; i < n; ++i) {
        int x, y; std::cin >> x >> y;
        ordered_x.push_back(Pair{x,y});
        ordered_y.push_back(Pair{x,y});
    }
    std::sort(ordered_x.begin(), ordered_x.end(), cmpx);
    std::sort(ordered_y.begin(), ordered_y.end(), cmpy);

    std::multiset<Pair, decltype(cmpx)> set(cmpx);
    ll answ = 0;
    for (int i = 0; i < n; ++i) {
        while ((int)set.size() < limit && !ordered_x.empty()) {
            auto p = ordered_x.back(); ordered_x.pop_back();
            if (p.y < ordered_y[i].y) continue;
            set.insert(p);
        }
        if ((int)set.size() == limit) {
            for (auto& it : set) {
                std::cout << it.x << ' ' << it.y << std::endl;
            }
            answ = std::max(answ, (ll) set.begin()->x * ordered_y[i].y);
            std::cout << "answ = " << answ << std::endl << std::string(80, '-') << std::endl;
        }
        if (i == 0 || ordered_y[i].y == ordered_y[i-1].y) {
            continue;
        }
        for (int j = i-1; j >= 0 && ordered_y[j].y == ordered_y[i-1].y; --j) {
            if (set.find(ordered_y[j]) != set.end()) {
                set.erase(ordered_y[j]);
            }
        }
    }
    std::cout << answ;
    return 0;
}