#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int nx=2e5+5;
ll n, m, cnt, ans;
map<ll, ll> mp;
struct cake
{
ll v, c, idx;
cake(): v(0), c(0), idx(0){}
bool operator< (const cake &o) const {return c<o.c;}
} c[nx];
struct persist
{
struct node
{
ll f, s;
node *l, *r;
node(ll f, ll s): f(f), s(s){}
};
typedef node* pnode;
pnode rt[nx];
void build(int l, int r, pnode &k)
{
k=new node(0, 0);
if (l==r) return;
int md=(l+r)/2;
build(l, md, k->l);
build(md+1, r, k->r);
k->f=k->l->f+k->r->f;
k->s=k->l->s+k->r->s;
}
void update(int l, int r, pnode &k, pnode t, int idx, ll vl)
{
k=new node(*t);
if (l==r) return k->f++, k->s+=vl, void();
int md=(l+r)/2;
if (idx<=md) update(l, md, k->l, t->l, idx, vl);
else update(md+1, r, k->r, t->r, idx, vl);
k->f=k->l->f+k->r->f;
k->s=k->l->s+k->r->s;
}
ll query2(int l, int r, pnode k, pnode t, ll key)
{
if (key==0||k->f-t->f==0) return 0;
if (l==r) return min(key, k->f-t->f)*((k->s)/(k->f));
int md=(l+r)/2;
if (k->r->f-t->r->f<key) return query2(l, md, k->l, t->l, key-(k->r->f-t->r->f))+k->r->s-t->r->s;
else return query2(md+1, r, k->r, t->r, key);
}
ll query(int l, int r)
{
return query2(1, n, rt[r], rt[l-1], m)-2*(c[r].c-c[l].c);
}
} s;
void solve(int l, int r, int optl, int optr)
{
if (r<l) return;
int md=(l+r)/2;
pair<ll, ll> mx={-1e18, 0};
for (int i=optl; i<=min(md-m+1, (ll)optr); i++) mx=max(mx, {s.query(i, md), i});
ans=max(ans, mx.first);
solve(l, md-1, optl, mx.second);
solve(md+1, r, mx.second, optr);
}
int main()
{
cin.tie(NULL)->sync_with_stdio(false);
cin>>n>>m;
for (int i=1; i<=n; i++) cin>>c[i].v>>c[i].c, mp[c[i].v]=0;
sort(c+1, c+n+1);
for (auto &[x, y]:mp) y=++cnt;
s.build(1, n, s.rt[0]);
for (int i=1; i<=n; i++) c[i].idx=mp[c[i].v];
for (int i=1; i<=n; i++) s.update(1, n, s.rt[i], s.rt[i-1], c[i].idx, c[i].v);
//for (int i=1; i<=n; i++) for (int j=i; j<=n; j++) cout<<"debug "<<i<<' '<<j<<' '<<s.query(i, j)<<'\n';
solve(m, n, 1, n);
cout<<ans;
}
