#include <bits/stdc++.h>
using namespace std;
#define short int32_t
#define int int64_t
#define long __int128_t
const int inf{numeric_limits<int>::max() / 4};
short main() {
#ifndef LOCAL
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
#endif
int n, m;
cin >> n >> m;
vector<pair<int, int>> pieces(n);
for (auto& [v, c] : pieces) {
cin >> v >> c;
}
sort(pieces.begin(), pieces.end(), [&](const auto& a, const auto& b) {
return a.second < b.second;
});
int v_sum{0};
int res{-inf};
for (int i{0}, j{0}; i + m <= n; i++) {
for (; j < i + m; j++) {
v_sum += pieces[j].first;
}
res = max(res, v_sum - (pieces[j - 1].second - pieces[i].second) * 2);
v_sum -= pieces[i].first;
}
cout << res << "\n";
return 0;
}
