//#define _GLIBCXX_DEBUG #include <bits/stdc++.h> #define int long long #define ld long double using namespace std; const int INF = 1e18; const int mod = 1e9+7; ld cost(int cnt_users,vector <pair<int,int>> &free,int need) { ld ans = 0; sort(free.begin(),free.end()); for (int i = 0;i < need;i++) { ans += free[i].first / (cnt_users * 1.0l); } return ans; } signed main() { mt19937 rng(69); int n,k; cin >> n >> k; vector <pair<int,int>> vec(n); vector <pair<int,int>> govno,good; for (int i = 0;i < n;i++) { cin >> vec[i].first >> vec[i].second; if (vec[i].second == -1) { govno.push_back(vec[i]); }else { good.push_back(vec[i]); } } sort(good.begin(),good.end(),[&] (pair<int,int> a,pair<int,int> b) { return a.second < b.second; }); ld best = INF; for (int cnt_support = 0;cnt_support <= good.size();cnt_support++) { vector <pair<int,int>> tmp; for (auto el : govno) { tmp.push_back(el); } ld ans = 0; for (int i = 0;i < cnt_support;i++) { ans += (good[i].second) / ((1 + i) * 1.0l); } for (int i = cnt_support;i < good.size();i++) { tmp.push_back(good[i]); } ans += cost(cnt_support + 1,tmp,max(0ll,k - cnt_support)); best = min(best,ans); } cout << best << "\n"; }