#include <bits/stdc++.h>
#define For(i,a,b) for(int i=a;i<=b;i++)
#define Forr(i,a,b) for(int i=a;i>=b;i--)
#define Fors(i,a,b,s) for(int i=a;i<=b;i+=s)
#define F first
#define S second
#define sz(x) ((int)x.size())
#define all(x) x.begin(),x.end()
#define eb emplace_back
#define INF (ll)(9e18)
#define endl '\n'
#define int double
using namespace std;
using pii=pair<int,int>;
int32_t main(){
ios::sync_with_stdio(false);
cin.tie(0);
set<int> data;
int N,K;
cin>>N>>K;;
vector<pii> cty;
vector<pii> clb;
int c=0;
for (int i=0;i<N;i++){
pii temp;
cin>>temp.F;
temp.S=i;
cty.push_back(temp);
cin>>temp.F;
if (temp.F!=-1){
clb.push_back(temp);
c+=1;
}
}
sort(cty.begin(),cty.end());
sort(clb.begin(),clb.end());
// for (int i=0;i<N;i++){
// cout<<cty[i].F<<" "<<cty[i].S<<endl;
// }
//
// for (int i=0;i<c;i++){
// cout<<clb[i].F<<" "<<clb[i].S<<endl;
// }
int ans=0;
for (int i=0;i<K;i++){
ans+=cty[i].F;
}
// cout<<min((int)c,(int)(K-1));
cout<<endl;
if (c==0){
cout<<ans;
}
else{
int temp=1;
int ansss=0;
int ub=min((int)c,(int)(K-1));
for (int i=0;i<ub;i++){
ansss+=(clb[i].F)/temp;
temp+=1;
int anss=ansss;
data.insert(clb[i].S);
int pn=temp-1;
int ct=0;
int id=0;
while (id<K-pn){
if (data.count(cty[ct].S)){
ct+=1;
continue;
}
else{
anss+=cty[ct].F/temp;
ct+=1;
id+=1;
}
}
if (anss<ans){
ans=anss;
}
}
cout<<ans;
}
}
