#include "bits/stdc++.h"
using namespace std;
#ifdef duc_debug
#include "bits/debug.h"
#else
#define debug(...)
#endif
const int maxn = 2e5 + 5;
int n, m, v[maxn], c[maxn];
int ord[maxn];
void solve() {
cin >> n >> m;
for (int i = 1; i <= n; ++i) {
cin >> v[i] >> c[i];
ord[i] = i;
}
sort(ord + 1, ord + n + 1, [](const int &x, const int &y) -> bool {
return c[x] < c[y];
});
set<pair<long long, int>> s;
long long sum = 0;
int cur_mn = 1;
set<int> cand;
for (int i = 1; i < m; ++i) {
if (i == 1) {
s.insert(make_pair(1ll * v[ord[i]] + 2 * c[ord[i]], i));
} else {
s.insert(make_pair(v[ord[i]], i));
}
cand.insert(i);
}
for (auto i:s) {
sum += i.first;
}
long long res = -1e18;
for (int i = m; i <= n; ++i) {
res = max(res, sum + v[ord[i]] - 2 * c[ord[i]]);
if (v[ord[i]] >= s.begin()->first) {
auto t = *s.begin();
s.erase(t);
cand.erase(t.second);
sum -= t.first;
sum += v[ord[i]];
s.insert(make_pair(v[ord[i]], i));
cand.insert(i);
if (t.second == cur_mn) {
cur_mn = *cand.begin();
s.erase(s.find(make_pair(v[ord[cur_mn]], cur_mn)));
s.insert(make_pair(1ll * v[ord[cur_mn]] + 2ll * c[ord[cur_mn]], cur_mn));
sum += 2ll * c[ord[cur_mn]];
}
}
}
cout << res;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
solve();
return 0;
}
