#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using t4=tuple<int,int,int,int>;
const int N=2e5+5;
const int K=1<<19;
const ll INF=LLONG_MAX/2;
int n,m;
int v[N],c[N],pos[N];
ll ans=-INF;
pair<int,int> a[N];
vector<pair<int,int>> vec;
struct Persist{
struct Node;
using Ptr = Node*;
struct Node{
ll val;
int freq;
Ptr l,r;
Node(ll val,int freq):val(val),freq(freq),l(nullptr),r(nullptr){}
};
Ptr rt[N];
void build(int l,int r,Ptr &t){
t=new Node(0,0);
if(l==r)return;
int m=(l+r)/2;
build(l,m,t->l);
build(m+1,r,t->r);
}
void build(int t){
build(1,n,rt[t]);
}
void update(int l,int r,Ptr &t,Ptr k,int x,ll v){
t=new Node(*k);
t->val+=v;
t->freq++;
if(l==r)return;
int m=(l+r)/2;
if(x<=m)update(l,m,t->l,k->l,x,v);
else update(m+1,r,t->r,k->r,x,v);
}
void update(int k,int t,int x,ll v){
update(1,n,rt[t],rt[k],x,v);
}
ll query(int l,int r,Ptr tl,Ptr tr,int k){
if(l==r)return tr->val-tl->val;
int m=(l+r)/2;
int freq=tr->r->freq-tl->r->freq;
if(freq<k)return query(l,m,tl->l,tr->l,k-freq)+tr->r->val-tl->r->val;
return query(m+1,r,tl->r,tr->r,k);
}
ll query(int l,int r,int k){
return query(1,n,rt[l-1],rt[r],k);
}
}s;
void dnc(int l,int r,int optl,int optr){
if(l>r)return;
int mid=(l+r)/2;
ll res=-INF;
int opt=-1;
int p=max(optl,mid+m-1);
for(int i=p;i<=optr;i++){
ll tmp=s.query(mid,i,m)-2*c[i];
if(tmp>res)res=tmp,opt=i;
}
res+=2*c[mid];
ans=max(ans,res);
dnc(l,mid-1,optl,opt);
dnc(mid+1,r,opt,optr);
}
int main(){
cin.tie(nullptr)->sync_with_stdio(false);
cin >> n >> m;
for(int i=1;i<=n;i++)cin >> a[i].second >> a[i].first;
sort(a+1,a+n+1);
for(int i=1;i<=n;i++){
tie(c[i],v[i])=a[i];
vec.emplace_back(v[i],i);
}
sort(vec.begin(),vec.end());
for(int i=0;i<n;i++)pos[vec[i].second]=i+1;
s.build(0);
for(int i=1;i<=n;i++)s.update(i-1,i,pos[i],v[i]);
dnc(1,n-m+1,1,n);
cout << ans;
}
