#include <bits/stdc++.h>
#define int long long
#define C first
#define V second
using namespace std;
typedef pair<int,int> ii;
signed main(){
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
int n, m; cin >> n >> m;
ii arr[n];
for(int i = 0;i < n;i++) cin >> arr[i].V >> arr[i].C;
sort(arr,arr+n);
int ans = 0;
for(int s = 0;s < n;s++){
priority_queue<int, vector<int>, greater<int> > pq;
int acc = 0;
for(int e = s+1;e < n;e++){
if((int) pq.size() >= m - 2){
if((int) pq.size() > m - 2){
acc -= pq.top();
pq.pop();
}
ans = max(ans, acc + arr[s].V + arr[e].V - 2*arr[e].C + 2*arr[s].C);
}
pq.push(arr[e].V);
acc += arr[e].V;
}
}
cout << ans;
}
