#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3,unroll-loops")
#define int long long
#define ii pair<int,int>
#define fir first
#define sec second
#define pb push_back
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
int n,m;
cin>>n>>m;
ii apa[n+1];
for(int q=1;q<=n;q++){
cin>>apa[q].sec>>apa[q].fir;
}
sort(apa+1,apa+n+1);
int ans=-1e18;
for(int q=1;q<=n-m+1;q++){
int tot=apa[q].sec+2*apa[q].fir;
priority_queue<int,vector<int>,greater<int> >pq;
for(int w=q+1;w<=n;w++){
pq.push(apa[w].sec);
tot+=apa[w].sec;
if(pq.size()>m-1){
tot-=pq.top(); pq.pop();
}
if(pq.size()>=m-1){
ans=max(ans,tot-2*apa[w].fir);
}
}
}
cout<<ans<<endl;
}
