#include <bits/stdc++.h>
using namespace std;
#define ar array
#define sz(v) int(std::size(v))
using i64 = long long;
const int N = 2e5, N_ = 1 << 18;
const i64 INF = 1e18;
int n, m;
int v[N], c[N], order[N];
vector<int> vv;
i64 best[N];
struct {
i64 sum[N_ * 2]; int cnt[N_ * 2];
void inc(int i, int x) {
i += N_;
sum[i] += x * vv[i - N_];
cnt[i] += x;
while (i /= 2) sum[i] = sum[i * 2] + sum[i * 2 + 1], cnt[i] = cnt[i * 2] + cnt[i * 2 + 1];
}
i64 qry(int x) {
int i = 1;
i64 s = 0;
assert(m <= cnt[1]);
while (i < N_) {
if (cnt[i * 2 + 1] <= x) {
x -= cnt[i * 2 + 1];
s += sum[i * 2 + 1];
i *= 2;
} else i = i * 2 + 1;
}
assert(cnt[i] >= x);
s += (i64) x * vv[i - N_];
return s;
}
} seg;
int pl = 0, pr = -1;
void upd(int i, int x) {
seg.inc(order[i], x);
}
i64 qry(int l, int r) {
if (r - l + 1 < m) return -INF;
while (pl > l) upd(--pl, 1);
while (pl < l) upd(pl++, -1);
while (pr > r) upd(pr--, -1);
while (pr < r) upd(++pr, 1);
return seg.qry(m) - 2 * (c[r] - c[l]);
}
void rec(int l, int r, int low, int hi) {
if (l <= r) {
int m = (l + r) / 2, opt = low;
best[m] = qry(m, opt);
for (int i = low + 1; i <= hi; i++) {
i64 x = qry(m, i);
if (x > best[m]) best[m] = x, opt = i;
}
rec(l, m - 1, low, opt);
rec(m + 1, r, opt, hi);
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> m;
vector<pair<int, int>> tmp;
for (int i = 0; i < n; i++) {
int v, c; cin >> v >> c;
tmp.push_back({c, v});
vv.push_back(v);
}
sort(begin(tmp), end(tmp));
sort(begin(vv), end(vv));
vv.erase(unique(begin(vv), end(vv)), end(vv));
for (int i = 0; i < n; i++) {
tie(c[i], v[i]) = tmp[i];
order[i] = lower_bound(begin(vv), end(vv), v[i]) - begin(vv);
}
rec(0, n - m, 0, n - 1);
cout << *max_element(best, best + n - m + 1) << '\n';
}
