#include <bits/stdc++.h>   using namespace std;   using ll = long long;   const int nax = 2e5 + 10;   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     int n, f;     cin >> n >> f;     vector<int> k(n), l(n);     vector<pair<int, int> > a;     for (int i = 0; i < n; i++) {       cin >> k[i] >> l[i];       a.push_back({min(2 * k[i], l[i]) - min(k[i], l[i]), i});     }     sort(a.rbegin(), a.rend());     ll ans = 0;     for (int i = 0; i < f; i++) {       ans += min(2 * k[a[i].second], l[a[i].second]);     }     for (int i = f; i < n; i++) {       ans += min(k[a[i].second], l[a[i].second]);     }     cout << ans <<   n ;     return 0;   }   