#pragma GCC Optimize("Ofast")

#include <bits/stdc++.h>

#define all(x) begin(x),end(x)

using namespace std;
using ld = long double;
using ll = long long;

const bool LOCAL = true;

void solve() {
  int n, k;
  cin >> n >> k;
  vector<pair<int, int>> arr(n);
  map<int, map<int, int>> weightToCountedColors; // weight -> {color -> count}
  for (int i = 0; i < n; i++) {
    cin >> arr[i].first >> arr[i].second; // weight, color
    weightToCountedColors[arr[i].first][arr[i].second]++;
  }

  // block = a set of elements with the same weight
  // multiblock = block with elements with at least two different colors
  // simpleblock = block with elements with only one color (<=> number of elements in the block is one)

  vector<pair<int, map<int, int>>> blocks;

  for (auto &element: weightToCountedColors) {
    auto &weight = element.first;
    auto &block = element.second;

    if (block.size() >= 2) {
      blocks.emplace_back(weight, block); // current block is multiblock
      continue;
    }

    block.begin()->second = 1; // current block is a simpleblock, so we need to set number of elements to 1
    int currentColor = block.begin()->first;

    if (blocks.empty() || blocks.back().second.size() >= 2) {
      blocks.emplace_back(weight, block); // previous block is a multiblock or it is first element
      continue;
    }

    if (blocks.back().second.begin()->first == currentColor) {
      blocks.back().first = weight; // previous block is a simpleblock with the same color as current
    } else {
      blocks.emplace_back(weight, block); // previous block is a simpleblock with another color
    }
  }

  // The size of answer must be equal to at most k

  long long answer = 0;
  int currentSize = 0;
  for (auto it = blocks.rbegin(); it != blocks.rend(); it++) {
    auto &weight = it->first;
    auto &block = it->second;

    for (auto element: block) {
      auto count = element.second;
      currentSize += count;
      answer += 1ll * count * weight;
    }

    if (currentSize >= k) {
      while (currentSize > k) {
        currentSize--;
        answer -= weight;
      }
      break;
    }
  }

  cout << answer << '\n';
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  if (LOCAL) {
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
  }

  solve();
}