Problem: You have a playlist consisting of n songs. The i-th song is characterized by two numbers t_i and b_i — its length and beauty respectively. The pleasure of listening to set of songs is equal to the total length of the songs in the set multiplied by the minimum beauty among them. For example, the pleasure of listening to a set of 3 songs having lengths [5, 7, 4] and beauty values [11, 14, 6] is equal to (5 + 7 + 4) ⋅ 6 = 96.

You need to choose at most k songs from your playlist, so the pleasure of listening to the set of these songs them is maximum possible.

Input

The first line contains two integers n and k (1 ≤ k ≤ n ≤ 3 ⋅ 10^5) – the number of songs in the playlist and the maximum number of songs you can choose, respectively.

Each of the next n lines contains two integers t_i and b_i (1 ≤ t_i, b_i ≤ 10^6) — the length and beauty of i-th song.

Output

Print one integer — the maximum pleasure you can get.

Examples

Input


4 3
4 7
15 1
3 6
6 8


Output


78


Input


5 3
12 31
112 4
100 100
13 55
55 50


Output


10000

Note

In the first test case we can choose songs {1, 3, 4}, so the total pleasure is (4 + 3 + 6) ⋅ 6 = 78.

In the second test case we can choose song 3. The total pleasure will be equal to 100 ⋅ 100 = 10000.

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
long long Gcd(long long a, long long b) {
  if (a % b == 0) return b;
  return Gcd(b, a % b);
}
long long Max(long long a, long long b) {
  if (a > b) return a;
  return b;
}
long long Min(long long a, long long b) {
  if (a < b) return a;
  return b;
}
long long findlcm(vector<long long> arr, long long n) {
  long long ans = arr[0];
  for (int i = 1; i < n; i++) ans = (((arr[i] * ans)) / (Gcd(arr[i], ans)));
  return ans;
}
long long gcdExtended(long long a, long long b, long long *x, long long *y) {
  if (a == 0) {
    *x = 0, *y = 1;
    return b;
  }
  long long x1, y1;
  long long gcd = gcdExtended(b % a, a, &x1, &y1);
  *x = y1 - (b / a) * x1;
  *y = x1;
  return gcd;
}
long long power(long long x, long long y, long long p) {
  long long res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
long long modInverse(long long a, long long m) {
  long long x, y;
  long long g = gcdExtended(a, m, &x, &y);
  if (g != 1)
    return -1;
  else {
    long long res = (x % m + m) % m;
    return res;
  }
}
vector<long long> primeFactors(long long n) {
  vector<long long> v;
  while (n % 2 == 0) {
    v.push_back(2);
    n = n / 2;
  }
  for (int i = 3; i <= sqrt(n); i = i + 2) {
    while (n % i == 0) {
      v.push_back(i);
      n = n / i;
    }
  }
  if (n > 2) v.push_back(n);
  return v;
}
long long binarySearch(long long arr[], long long l, long long r, long long x) {
  if (r >= l) {
    long long mid = l + (r - l) / 2;
    if (arr[mid] == x) return mid;
    if (arr[mid] > x) return binarySearch(arr, l, mid - 1, x);
    return binarySearch(arr, mid + 1, r, x);
  }
  return -1;
}
vector<long long> shortPath(vector<pair<long long, long long>> v[],
                            long long src, long long V = 0) {
  set<pair<long long, long long>> setds;
  long long sizee = V;
  long long IN = 0x3f3f3f3f;
  vector<long long> dist(sizee, IN);
  setds.insert(make_pair(0, src));
  dist[src] = 0;
  while (!setds.empty()) {
    pair<long long, long long> tmp = *(setds.begin());
    cout << tmp.first << " ";
    setds.erase(setds.begin());
    long long u = tmp.second;
    vector<pair<long long, long long>>::iterator i;
    for (i = v[u].begin(); i != v[u].end(); ++i) {
      long long v = (*i).first;
      long long weight = (*i).second;
      if (dist[v] > dist[u] + weight) {
        if (dist[v] != 0x3f3f3f3f)
          setds.erase(setds.find(make_pair(dist[v], v)));
        dist[v] = dist[u] + weight;
        setds.insert(make_pair(dist[v], v));
      }
    }
  }
  return dist;
}
void dfs(std::vector<long long> v[], long long s, bool visited[]) {
  cout << s + 1 << " ";
  visited[s] = true;
  for (long long i = 0; i < v[s].size(); ++i) {
    if (!visited[v[s][i]]) {
      dfs(v, v[s][i], visited);
    }
  }
}
void bfs(vector<long long> adj[], long long s, bool visited[]) {
  long long ret = 0;
  list<int> queue;
  visited[s] = true;
  queue.push_back(s);
  list<int>::iterator i;
  vector<long long>::iterator j;
  while (!queue.empty()) {
    s = queue.front();
    cout << s + 1 << " ";
    ret++;
    queue.pop_front();
    for (j = adj[s].begin(); j != adj[s].end(); ++j) {
      if (!visited[*j]) {
        visited[*j] = true;
        queue.push_back(*j);
      }
    }
  }
}
void printgraph(std::vector<long long> v[], long long n) {
  for (long long i = 0; i < n; i++) {
    for (auto l = v[i].begin(); l != v[i].end(); l++) {
      cout << i << " " << *l << endl;
    }
  }
}
void printvector(std::vector<long long> v) {
  for (auto i = v.begin(); i != v.end(); i++) cout << *i << " ";
  cout << "" << endl;
}
void printarray(long long arr[], long long n) {
  for (long long i = 0; i < n; i++) cout << arr[i] << " ";
  cout << "" << endl;
}
void printarray(double arr[], long long n) {
  for (long long i = 0; i < n; i++) cout << arr[i] << " ";
  cout << "" << endl;
}
void printarray(bool arr[], long long n) {
  for (long long i = 0; i < n; i++) cout << arr[i] << " ";
  cout << "" << endl;
}
void weightedgraph(std::vector<pair<long long, long long>> v[], long long n) {
  for (long long i = 0; i < n; i++) {
    for (auto j = v[i].begin(); j != v[i].end(); j++) {
      cout << i << " " << (*j).first << " " << (*j).second << endl;
    }
  }
}
void solve() {
  priority_queue<long long, std::vector<long long>, greater<long long>> pq;
  long long n, k;
  cin >> n >> k;
  std::vector<pair<long long, long long>> v;
  long long i, j;
  for (i = 0; i < n; i++) {
    long long l, b;
    cin >> l >> b;
    v.push_back(make_pair(b, l));
  }
  sort(v.begin(), v.end());
  long long sum = 0;
  long long ans = 0;
  for (i = n - 1; i >= 0; i--) {
    sum += v[i].second;
    pq.push(v[i].second);
    while (pq.size() > k) {
      long long top = pq.top();
      pq.pop();
      sum -= top;
    }
    ans = Max(ans, sum * v[i].first);
  }
  cout << ans << endl;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  solve();
}