#include <bits/stdc++.h> using namespace std; #define int long long #define pll pair<long long, long long> #define mp make_pair #define pb push_back #define f first #define s second #define endl '\n' #define ld long double #define sz(x) static_cast<int>((x).size()) #define i5 tuple<int,int,int,int,int> #define all(x) x.begin(), x.end() #define iiii tuple<int, int,int,int> #define ld long double signed main(){ int n,k,c=0;cin>>n>>k; vector<pll> v(n); for(int i=0;i<n;i++){ cin>>v[i].s>>v[i].f; if(v[i].f == -1){ v[i].f=1e9; } else c++; } sort(all(v), [&](pll a, pll b){ if(a.f==b.f)return a.s > b.s; else return a.f < b.f; }); ld ans=1e9; for(int i=0;i<=c;i++){ ld cur=0; for(int j=0;j<i;j++){ cur += v[j].f / (ld)(j+1); } vector<int> t; for(int j=i;j<n;j++){ t.pb(v[j].s); } sort(all(t)); for(int j=0;j<k-i;j++){ cur+=(t[j] / (ld)(i+1)); } ans=min(ans, cur); } cout<<fixed<<ans; }