#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
const ll inf=1e18;
const int N=200050;
const int M=20*N;
int v[N],c[N],id[N],idv[N],pos[N],n,m;
int ls[M],rs[M],tsz,root[N],sz[M];
ll sum[M];
void Set(int p, int &c, int ss, int se, int qi, ll x)
{
c=++tsz;ls[c]=ls[p];rs[c]=rs[p];sum[c]=sum[p]+x;sz[c]=sz[p]+1;
if(ss==se) return;
int mid=ss+se>>1;
if(qi<=mid) Set(ls[p],ls[c],ss,mid,qi,x);
else Set(rs[p],rs[c],mid+1,se,qi,x);
}
ll Get(int p, int c, int ss, int se, int k)
{
ll ans=0;
while(1)
{
if(ss==se){ if(k>0) ans+=sum[c];break;}
int mid=ss+se>>1;
int A=sz[ls[c]]-sz[ls[p]];
if(A<=k) k-=A,ans+=sum[ls[c]]-sum[ls[p]],ss=mid+1,p=rs[p],c=rs[c];
else se=mid,p=ls[p],c=ls[c];
}
return ans;
}
ll Get(int l, int r)
{
return v[id[l]]+c[id[l]]+v[id[r]]-c[id[r]]+Get(root[l],root[r-1],1,n,m-2);
}
int nxt[N],pre[N];
vector<int> work[N];
void Del(int x)
{
int l=pre[x],r=nxt[x];
pre[x]=nxt[x]=0;
nxt[l]=r;
pre[r]=l;
}
void Add(int x)
{
int las=pre[0];
nxt[las]=x;
pre[x]=las;
pre[0]=x;
nxt[x]=0;
}
int main()
{
scanf("%i %i",&n,&m);
for(int i=1;i<=n;i++) scanf("%i %i",&v[i],&c[i]),c[i]*=2,id[i]=idv[i]=i;
sort(id+1,id+1+n,[&](int i, int j){ return c[i]<c[j];});
sort(idv+1,idv+1+n,[&](int i, int j){ return v[i]>v[j];});
for(int i=1;i<=n;i++) pos[idv[i]]=i;
for(int i=1;i<=n;i++) Set(root[i-1],root[i],1,n,pos[id[i]],v[id[i]]);
vector<int> L,R;
for(int i=1;i<=n;i++) if(i==1 || v[id[i]]+c[id[i]]>v[id[L.back()]]+c[id[L.back()]]) L.pb(i);
for(int i=n;i>=1;i--) if(i==n || v[id[i]]-c[id[i]]>v[id[R.back()]]-c[id[R.back()]]) R.pb(i);
reverse(R.begin(),R.end());
ll ans=-inf;
for(int i=0,j=0;i<R.size();i++)
{
while(j<L.size() && R[i]-L[j]+1>=m)
{
Add(L[j]);
work[i].pb(L[j]);
j++;
}
reverse(work[i].begin(),work[i].end());
for(int x:work[i])
{
while(pre[x]!=0 && Get(pre[x],R[i])<=Get(x,R[i])) Del(pre[x]);
if(pre[x]!=0)
{
int top=(int)R.size()-1,bot=i+1,mid,ans=-1;
while(top>=bot)
{
mid=top+bot>>1;
if(Get(pre[x],R[mid])<=Get(x,R[mid])) ans=mid,top=mid-1;
else bot=mid+1;
}
if(ans!=-1) work[ans].pb(x);
else Del(x);
}
}
if(nxt[0]!=0) ans=max(ans,Get(nxt[0],R[i]));
}
printf("%lld\n",ans);
return 0;
}
