#pragma GCC optimize("O3,unroll-loops")
#include<stdio.h>
#include<time.h>
#include<stdlib.h>
#define N 200000
int n, M, v[N],c[N],o[N],v2[N],vm[N],fw[N];
long long fw2[N],z=-1e18;
void add_(int p,int k1,long long k2) { for(;p<N;p|=p+1)fw[p]+=k1,fw2[p]+=k2; }
long long search()
{
long long val2=0;int val=0,pos=0;
for(int j=1<<20;j>>=1;)
if(pos+j<=N&&val+fw[pos+j-1]<=M)pos+=j,val+=fw[pos-1],val2+=fw2[pos-1];
return val2;
}
int cl=0,cr=-1;
void add(int i) { add_(vm[i],1,v[i]); }
void del(int i) { add_(vm[i],-1,-v[i]); }
void move(int l,int r)
{
while(cr<r)add(++cr);
while(cl>l)add(--cl);
while(cr>r)del(cr--);
while(cl<l)del(cl++);
}
void map(int i)
{
int lb=-1,ub=n,x=v[i];
while(ub-lb>1)
{
int mid=lb+(ub-lb)/2;
if(v2[mid]<x)lb=mid;
else ub=mid;
}
vm[i]=n-ub-1;
}
void sort(int *a,int l,int r)
{
while(l<r)
{
int i=l,j=l,k=r,t,p=a[l+rand()%(r-l)];
while(j<k)
{
int cmp;
if(a==v2)cmp=a[j]-p;
else cmp=c[a[j]]-c[p];
if(cmp<0)
t=a[i],a[i]=a[j],a[j]=t,++i,++j;
else if(cmp==0)
++j;
else
t=a[--k],a[k]=a[j],a[j]=t;
}
sort(a,l,i);
l=k;
}
}
void dnc(int l,int r,int optl,int optr)
{
if(l>r) return;
int m=l+(r-l)/2,opt=-1;
long long res=-1e18,res2;
for(int i=optl;i<=optr&&i+M-1<=m;++i)
{
move(i,m);
res2=search()-2*(c[m]-c[i]);
if(res2>res)res=res2,opt=i;
}
if(res>z)z=res;
dnc(l,m-1,optl,opt);
dnc(m+1,r,opt,optr);
}
int main()
{
srand(time(0));
scanf("%d%d",&n,&M);
for(int i=0;i<n;++i)scanf("%d%d",v+i,c+i),o[i]=i;
sort(o,0,n);
for(int i=0;i<n;++i)v2[i]=v[o[i]],vm[i]=c[o[i]];
for(int i=0;i<n;++i)c[i]=vm[i],v[i]=v2[i],o[i]=i;
sort(v2,0,n);
for(int i=0;i<n;++i)
{
map(i);
/* duplicate element break fenwick search */
vm[i]-=o[vm[i]]++;
}
dnc(M-1,n-1,0,n-1);
printf("%lld",z);
}
