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

using namespace std;

struct Jewel {
    int price;
    int weight;
};

int n, k;
Jewel js[2000000];

pair<long long, long long> pickLinear(long long s, long long w, int start,
                                      int end) {
    int bestJ = start;
    long long sBest = s + js[start].price;
    long long wBest = w + js[start].weight;

    // printf("%lf ", sBest / wBest);
    for (int j = start + 1; j <= end; j++) {
        double v = ((double)(s + js[j].price)) / (w + js[j].weight);

        if (v > ((double)sBest) / wBest) {
            sBest = s + js[j].price;
            wBest = w + js[j].weight;
            bestJ = j;
        }

        // printf("%lf ", v);
    }
    // puts("");

    swap(js[n - 1], js[bestJ]);
    n--;

    return {sBest, wBest};
}

pair<long long, long long> pick(double s, double w) {
    int lo = 0;
    int hi = n - 1;

    int bestJ;
    long long sBest;
    long long wBest;

    while (lo <= hi) {
        int mid = (lo + hi) / 2;
        double v = ((double)(s + js[mid].price)) / (w + js[mid].weight);

        // cout << lo << ' ' << hi << '\n';

        // for (int i = lo; i <= hi; i++) {
        //     printf("%lf ", (s + js[i].price) / (w + js[i].weight));
        // }
        // puts("");

        if (hi - lo <= 100) {
            return pickLinear(s, w, lo, hi);
        }

        double prevV =
            ((double)(s + js[mid - 1].price)) / (w + js[mid - 1].weight);
        double nextV =
            ((double)(s + js[mid + 1].price)) / (w + js[mid + 1].weight);
        if (prevV <= v && v >= nextV) {
            bestJ = mid;
            sBest = s + js[mid].price;
            wBest = w + js[mid].price;
            break;
        } else if (prevV > v) {
            hi = mid;
        } else {
            lo = mid;
        }
    }

    swap(js[n - 1], js[bestJ]);
    n--;

    return {sBest, wBest};
}

long long solve() {
    long long s = 0;
    long long w = 0;
    int size = n;

    // sort(js.begin(), js.end(), [](const Jewel &a, const Jewel &b) {
    sort(js, js + n, [](const Jewel &a, const Jewel &b) {
        return (((double)a.price) / a.weight > ((double)b.price) / b.weight)
        ||
               a.price > b.price;
    });

    puts("Sorted");

    if (k > n) {
        return 0;
    }

    if (k == n) {
        for (Jewel &b : js) {
            s += b.price;
        }
        return s;
    }

    for (int i = 0; i < k; i++) {
        pair<long long, long long> picked = pick(s, w);
        s = picked.first;
        w = picked.second;
    }

    return s;
}

int main() {
    scanf("%d%d", &n, &k);

    // js.resize(n);
    for (int i = 0; i < n; i++) {
        Jewel &j = js[i];
        scanf("%d%d", &j.price, &j.weight);
    }

    // puts("Done reading");

    long long res = solve();
    printf("%lld", res);

    return 0;
}