#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define AquA cin.tie(0);ios_base::sync_with_stdio(0);
#define fs first
#define sc second
#define p_q priority_queue
using namespace std;
/*
Cake: idk
LCBorz
*/
int main(){
AquA;
int n,m;
cin >> n >> m;
vector<pair<int,int> > v(n);
for(int i=0;i<n;i++){
cin >> v[i].fs >> v[i].sc;
}
sort(v.begin(),v.end(),[&](pair<int,int> a,pair<int,int> b){return a.sc<b.sc;});
long long ans=-1e18;
for(int i=m-1;i<n;i++){
p_q<int,vector<int>,greater<int> > pq;
long long sum=0;
int cnt=0;
for(int j=i;j>=0;j--){
cnt++;
sum+=v[j].fs;
pq.push(v[j].fs);
if(cnt>m){
cnt--;
sum-=pq.top();
pq.pop();
}
if(cnt>=m){
ans=max(ans,sum-2*(v[i].sc-v[j].sc));
}
}
}
cout << ans << "\n";
return 0;
}
