#include <bits/stdc++.h>
#define int long long
using namespace std;
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, m; cin >> n >> m;
vector<pair<int, int>> a(n);
for (auto &[c, v] : a)
cin >> v >> c;
sort(a.begin(), a.end());
int ans = LLONG_MIN;
for (int l = 0; l < n; l++) {
priority_queue<int, vector<int>, greater<int>> pq;
int curr = 0;
for (int r = l; r < n; r++) {
pq.push(a[r].second);
curr += a[r].second;
while ((int)pq.size() > m) {
curr -= pq.top();
pq.pop();
}
if ((int)pq.size() == m)
ans = max(ans, curr - 2*(a[r].first - a[l].first));
}
}
cout << ans << endl;
return 0;
}
