# include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF=1e18;
int n,m,len,vv[200010],rt[200010],lc[4000010],rc[4000010],cnt[4000010],tot=1;
ll sum[4000010],ans=-INF;
struct node
{
	int V,C;
	bool operator<(const node &a)const{return C<a.C;}
}a[200010];
void update(int &rt,int l,int r,int x)
{
	cnt[++tot]=cnt[rt];sum[tot]=cnt[rt];lc[tot]=lc[rt];rc[tot]=rc[rt];rt=tot;
	if(l==r) return cnt[rt]++,sum[rt]+=vv[l],void();
	int mid=(l+r)/2;
	if(x<=mid) update(lc[rt],l,mid,x);
	else update(rc[rt],mid+1,r,x);
	cnt[rt]=cnt[lc[rt]]+cnt[rc[rt]];
	sum[rt]=sum[lc[rt]]+sum[rc[rt]];
}
ll query(int rt1,int rt2,int l,int r,int x)
{
	if(l==r) return (ll)x*vv[l];
	int mid=(l+r)/2;
	if(cnt[rc[rt2]]-cnt[rc[rt1]]>=x) return query(rc[rt1],rc[rt2],mid+1,r,x);
	else return query(lc[rt1],lc[rt2],l,mid,x-(cnt[rc[rt2]]-cnt[rc[rt1]]))+sum[rc[rt2]]-sum[rc[rt1]];
}
ll W(int i,int j)
{
	if(i>j || cnt[rt[j]]-cnt[rt[i-1]]<m) return -INF;
	return query(rt[i-1],rt[j],1,len,m)+2*a[i].C-2*a[j].C;
}
void solve(int l,int r,int x,int y)
{
	if(l>r) return;
	int mid=(l+r)/2,p=0;
	ll maxn=-INF,t;
	for(int i=x;i<=y && i<=mid-m+1;i++)
		if((t=W(i,mid))>maxn) maxn=t,p=i;
	ans=max(ans,maxn);
	solve(l,mid-1,x,p);solve(mid+1,r,p,y);
}
int main()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++) scanf("%d%d",&a[i].V,&a[i].C),vv[++len]=a[i].V;
	sort(a+1,a+n+1);
	sort(vv+1,vv+len+1);
	len=unique(vv+1,vv+len+1)-vv-1;
	auto get=[](int v){return lower_bound(vv+1,vv+len+1,v)-vv;};
	for(int i=1;i<=n;i++) a[i].V=get(a[i].V);
	for(int i=1;i<=n;i++) update(rt[i]=rt[i-1],1,len,a[i].V);
	solve(m,n,1,n-m+1);
	cout<<ans<<endl;
	return 0;
}