#include <bits/stdc++.h>
using namespace std;
#define finish(x) return cout << x << endl, 0
#define ll long long
int n, m;
vector <pair <int, int> > a;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
a.resize(n);
for(auto &i : a) cin >> i.second >> i.first;
sort(a.begin(), a.end());
multiset <int> s;
ll sum = 0;
ll ans = 0;
for(int i = 0 ; i < n ; i++){
for(int j = i + 1 ; j < n ; j++){
if((int)s.size() == m - 2){
ans = max(ans, a[i].second - 2 * a[i].first + sum + a[j].first - 2 * a[j].first);
}
s.insert(a[j].second);
sum += a[j].second;
if((int)s.size() > m - 2){
sum -= *s.begin();
s.erase(s.begin());
}
}
}
cout << ans << endl;
}
