#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = 2e5+3;
ll i,j,p,q,n,m,k,v[maxn],c[maxn];
pair <ll,ll> inp[maxn];
set < pair <ll,int> > vals;
set < pair<ll,int> > :: iterator it;
ll sum = 0;
bool fl = false;
int l,r;
void add(ll val,int ind)
{
if(vals.size()<m-2)
{
vals.insert({val,ind});
sum+=val;
if(vals.size()==m-2)
fl = true,it = vals.begin();
return ;
}
if((*it).first>=val)
vals.insert({val,ind});//dano ne pravi problemi s it
if((*it).first<val)
{
sum -= (*it).first;
sum += val;
vals.insert({val,ind});
it++;
}
}
void rem(ll val,int ind)
{
if(vals.size()<=m-2)
{
vals.erase({val,ind});
sum-=val;
fl = false;
return ;
}
//dano ne pravi problemi s it
if((*it).first>val)
{
vals.erase({val,ind});
}
if((*it).first<=val)
{
sum -= val;
it--;
sum+=(*it).first;
vals.erase({val,ind});
}
}
void activate(int ll,int rr)
{
while(r<rr)
{
r++;
add(v[r],r);
}
//cout<<l<<" "<<r<<" "<<sum<<endl;
while(ll<l)
{
l--;
add(v[l],l);
}
//cout<<l<<" "<<r<<" "<<sum<<endl;
while(ll>l)
{
rem(v[l],l);
l++;
}
//cout<<l<<" "<<r<<" "<<sum<<endl;
while(rr<r)
{
rem(v[r],r);
r--;
}
//cout<<l<<" "<<r<<" "<<sum<<endl;
//cout<<fl<<" "<<sum<<endl;
}
ll overall;
void solve(int l,int r,int optl,int optr)
{
if(r<l)return;
int mid = (l+r)/2;
ll ans = -1e18;
int pos;
for(int i=optl; i<=min(mid,optr); i++)
{
// cout<<i+1<<" "<<mid-1<<" managed :"<<endl;
ll tek =v[i]+v[mid] - 2*(c[mid] - c[i]);
if(i+1<=mid-1)activate(i+1,mid-1);
if(fl)
tek+=sum;
else tek-=1e18;
// cout<<tek<<endl;
if(tek>ans)
{
pos = i;
ans = tek;
}
}
overall = max(overall,ans);
solve(l,mid-1,optl,pos);
solve(mid+1,r,pos,optr);
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin>>n>>m;
for(i=1; i<=n; i++)
{
cin>>inp[i].second>>inp[i].first;
}
//cout<<endl;
sort(inp+1,inp+n+1);
for(i=1; i<=n; i++)
{
v[i] = inp[i].second;
c[i] = inp[i].first;
// cout<<v[i]<<" "<<c[i]<<endl;
}
sum = v[1];
l=r=1;
vals.insert({v[1],1});
it = vals.begin();
solve(1,n,1,n);
cout<<overall<<endl;
return 0;
}
