#include <bits/stdc++.h>
using namespace std;
#define TRACE(x) cerr << #x << " :: " << x << endl
#define _ << " " <<
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for(int i=(a);i>=(b);--i)
#define SZ(x) ((int)(x).size())
#define ALL(x) (x).begin(),(x).end()
const int mxN = 2e5+5;
int N, M;
struct Cake { int V, C; } cake[mxN];
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cin >> N >> M;
FOR(i,1,N){
int V, C; cin >> V >> C;
cake[i] = {V,C};
}
sort(cake+1,cake+1+N,[](Cake a, Cake b){ return a.C != b.C ? a.C < b.C : a.V < b.V; });
long long ans = 0;
FOR(l,1,N){
multiset<int> ms;
long long cur = 0;
FOR(r,l,N){
if (SZ(ms) < M) ms.insert(cake[r].V), cur += cake[r].V;
else if (cake[r].V > *ms.begin()) {
cur -= *ms.begin();
ms.erase(ms.begin());
ms.insert(cake[r].V);
cur += cake[r].V;
}
if (SZ(ms) == M) {
ans = max(ans,cur-2*(cake[r].C-cake[l].C));
}
}
}
cout << ans << '\n';
}
