#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 2e5 + 5;
int n, m;
pair <int, int> a[N];
int32_t main(){
cin.tie(NULL)->sync_with_stdio(false);
cin >> n >> m;
for (int i = 1; i <= n; i++) {
cin >> a[i].second >> a[i].first;
}
sort(a + 1, a + 1 + n);
int ans = 0, sum = 0;
multiset <int> ms;
for (int i = 1; i <= n; i++) {
ms.emplace(a[i].first);
sum += a[i].second;
if (i >= m) {
sum -= a[i - m].second;
ans = max(ans, sum - 2 * (*ms.rbegin() - *ms.begin()));
}
if (i > m) ms.erase(ms.find(a[i - m].first));
}
cout << ans;
}
