#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp> // Including tree_order_statistics_node_update
#define F first
#define S second
using namespace std;
using namespace __gnu_pbds;
typedef tree<
pair<int,int>,
null_type,
greater<pair<int,int> >,
rb_tree_tag,
tree_order_statistics_node_update>
ordered_set;
const int N=100005;
pair<int,int> arr[N];
long long diff[N],sdiff[N];
ordered_set ss;
vector<int> upd[N];
int n,m;
struct nodes{
long long val,lazy;
nodes():val(0),lazy(0){}
nodes(long long val):val(val),lazy(0){}
};
nodes operator +(const nodes &l,const nodes &r)
{
nodes res;
res.val=max(l.val,r.val);
res.lazy=0;
return res;
}
nodes btree[4*N];
void build(int node,int l,int r)
{
if(l==r)
{
btree[node]=nodes(sdiff[l]);
return;
}
int mid=(l+r)/2;
build(node*2,l,mid);
build(node*2+1,mid+1,r);
btree[node]=btree[node*2]+btree[node*2+1];
}
void down(int node,int l,int r)
{
if(btree[node].lazy)
{
btree[node].val+=btree[node].lazy;
if(l!=r)
{
btree[node*2].lazy+=btree[node].lazy;
btree[node*2+1].lazy+=btree[node].lazy;
}
btree[node].lazy=0;
}
}
void update(int node,int l,int r,int ind,long long val)
{
down(node,l,r);
if(ind<l||ind>r) return;
if(l==r)
{
btree[node]=nodes(btree[node].val+val);
sdiff[l]+=val;
return;
}
int mid=(l+r)/2;
update(node*2,l,mid,ind,val);
update(node*2+1,mid+1,r,ind,val);
btree[node]=btree[node*2]+btree[node*2+1];
}
void update(int node,int l,int r,int ql,int qr,long long val)
{
down(node,l,r);
if(r<ql||qr<l) return;
if(ql<=l&&r<=qr)
{
btree[node].lazy+=val;
down(node,l,r);
return;
}
int mid=(l+r)/2;
update(node*2,l,mid,ql,qr,val);
update(node*2+1,mid+1,r,ql,qr,val);
btree[node]=btree[node*2]+btree[node*2+1];
}
nodes query(int node,int l,int r,int ql,int qr)
{
down(node,l,r);
if(r<ql||qr<l) return nodes();
if(ql<=l&&r<=qr)
return btree[node];
int mid=(l+r)/2;
return query(node*2,l,mid,ql,qr)+query(node*2+1,mid+1,r,ql,qr);
}
void update(int x,long long val)
{
update(1,0,n-1,0,x,val);
}
int main()
{
scanf("%d %d",&n,&m);
for(int i=0;i<n;i++)
{
scanf("%d %d",&arr[i].S,&arr[i].F);
arr[i].F*=2;
}
sort(arr,arr+n);
long long cur=0,las=0;
// val = maxk(arr[i].S,arr[j].S) - arr[i].
for(int i=n-1;i>=0;i--)
{
ss.insert({arr[i].S,i});
if(ss.order_of_key({arr[i].S,i})<m)
{
cur+=arr[i].S;
if(ss.size()>m)
cur-=(*ss.find_by_order(m)).F;
}
else
{
upd[ss.order_of_key({arr[i].S,i})].push_back(i);
}
diff[i]=cur-las+arr[i].F-arr[i+1].F;
sdiff[i]=diff[i]+sdiff[i+1];
las=cur;
//cout << cur << " " << arr[i].F << " " << arr[i+1].F << " " << diff[i] << endl;
}
build(1,0,n-1);
int curp=m;
long long ans=-(1LL<<60);
for(int i=n-1;i>=m-1;i--)
{
//cout << query(1,0,n-1,i,i).val << " " << diff[i] << endl;
ans=max(ans,query(1,0,n-1,0,i-m+1).val-arr[i].F);
update(1,0,n-1,0,i-1,-arr[i].S);
//update(1,0,n-1,0,i-1,-diff[i]);
if(ss.order_of_key({arr[i].S,i})<m)
{
cur=0;
for(int j:upd[curp])
{
update(1,0,n-1,0,j,arr[j].S-cur);
cur=arr[j].S;
}
curp++;
}
ss.erase({arr[i].S,i});
}
printf("%lld\n",ans);
}
