#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcount
const int N = 2e5 + 7, INF = 1e18 + 7;
int n, m;
struct El { int v, c; } a[N];
struct Node { int cnt, sum; Node *l, *r; Node () { cnt = sum = 0; l = r = NULL; } };
vector <int> c;
Node *build(int tl, int tr) {
Node *ans = new Node();
if (tl == tr) return ans;
int tm = (tl + tr) >> 1;
ans->l = build(tl, tm); ans->r = build(tm + 1, tr);
return ans;
}
void relax(Node *t) { t->cnt = t->l->cnt + t->r->cnt; t->sum = t->l->sum + t->r->sum; }
Node *add(Node *t, int tl, int tr, int p) {
Node *ans = new Node();
if (tl == tr) { ans->cnt = t->cnt + 1; ans->sum = t->sum + c[p]; return ans; }
int tm = (tl + tr) >> 1;
if (p <= tm) { ans->l = add(t->l, tl, tm, p); ans->r = t->r; }
else { ans->l = t->l; ans->r = add(t->r, tm + 1, tr, p); }
relax(ans); return ans;
}
int get(Node *l, Node *r, int tl, int tr, int k) {
if (tl == tr) return c[tl] * k;
int tm = (tl + tr) >> 1;
int t = r->r->cnt - l->r->cnt;
if (k <= t) return get(l->r, r->r, tm + 1, tr, k);
else return get(l->l, r->l, tl, tm, k - t) + (r->r->sum - l->r->sum);
}
Node *t[N];
int get(int l, int r) {
return get(t[l - 1], t[r], 0, N, m) - 2 * (a[r].c - a[l].c);
}
int ans = -INF;
int get(int i, int l, int r) {
int best = -INF, pos = l;
for (int j = l; j <= r && m <= i - j + 1; ++j) {
int nn = get(j, i);
if (best < nn) { best = nn; pos = j; }
}
ans = max(ans, best);
return pos;
}
void solve(int l, int r, int ll, int rr) {
if (r < l) return;
int m = (l + r) >> 1; int mm = get(m, ll, rr);
if (l == r) return;
solve(l, m - 1, ll, mm); solve(m + 1, r, mm, rr);
}
bool comp(El a, El b) { return a.c < b.c; }
signed main() {
#ifdef HOME
freopen("input.txt", "r", stdin);
#else
ios_base::sync_with_stdio(0); cin.tie(0);
#endif
cin >> n >> m;
for (int i = 1; i <= n; ++i) { cin >> a[i].v >> a[i].c; c.app(a[i].v); }
sort(c.begin(), c.end()); c.resize(unique(all(c)) - c.begin());
sort(a + 1, a + n + 1, comp);
t[0] = build(0, N);
for (int i = 1; i <= n; ++i) {
t[i] = add(t[i - 1], 0, N, lower_bound(c.begin(), c.end(), a[i].v) - c.begin());
}
solve(1, n, 1, n); cout << ans << '\n';
}
