#include <bits/stdc++.h>
using namespace std;

const int N=200005;

struct Cake
{
	int c,v;
};

Cake a[N];

bool cmp(Cake a,Cake b)
{
	return a.c<b.c;
}

struct node
{
	int l,r,pos;
};

node q[N];
int c[N], v[N], n, m;
int rt[N], lc[N*35], rc[N*35], cnt[N*35], indx;
long long sum[N*35];

int update(int rt,int l,int r,int pos)
{
	int p=++indx;
	cnt[p]=cnt[rt]+1, lc[p]=lc[rt], rc[p]=rc[rt], sum[p]=sum[rt]+pos;
	if(l==r)
		return p;

	int mid=(l+r)/2;
	if(pos<=mid)
		lc[p]=update(lc[rt],l,mid,pos);
	else
		rc[p]=update(rc[rt],mid+1,r,pos);
	return p;
}

long long query(int rt1,int rt2,int l,int r,int k)
{
	if(l==r)
		return 1ll*k*l;

	int mid=(l+r)/2;
	if(cnt[rc[rt1]]-cnt[rc[rt2]]<k)
		return sum[rc[rt1]]-sum[rc[rt2]]+query(lc[rt1],lc[rt2],l,mid,k-(cnt[rc[rt1]]-cnt[rc[rt2]]));
	return query(rc[rt1],rc[rt2],mid+1,r,k);
}

long long calc(int l,int r)
{
	if(r-l+1<m)
		return 0xcfcfcfcfcfcfcfcf;

	return query(rt[r],rt[l-1],1,1000000000,m)-(c[r]-c[l])*2ll;
}

int main()
{
	cin >> n >> m;
	for(int i=1;i<=n;i++)
		scanf("%d %d",&a[i].v,&a[i].c);

	sort(a+1,a+n+1,cmp);

	for(int i=1;i<=n;i++)
		v[i]=a[i].v, c[i]=a[i].c;

	for(int i=1;i<=n;i++)
		rt[i]=update(rt[i-1],1,1000000000,v[i]);

	long long ans=0xcfcfcfcfcfcfcfcf;
	int l=1, r=0;
	q[++r]=(node){m,n,1};
	for(int i=m;i<=n;i++)
	{
		ans=max(ans,calc(q[l].pos,i));
		if(i!=n)
		{
			q[l].l++;
			if(q[l].l>q[l].r)
				l++;

			while(l<=r && calc(i-m+2,q[r].l)>=calc(q[r].pos,q[r].l))
				r--;

			if(l>r)
				q[++r]=(node){i+1,n,i-m+2};
			else
			{
				int L=q[r].l+1, R=q[r].r, lpos=q[r].r+1;
				while(L<=R)
				{
					int mid=(L+R)/2;
					if(calc(i-m+2,mid)>=calc(q[r].pos,mid))
						lpos=mid, R=mid-1;
					else
						L=mid+1;
				}

				q[r].r=lpos-1;
				if(lpos<=n)
					q[++r]=(node){lpos,n,i-m+2};
			}
		}
	}
	printf("%lld\n",ans);
	return 0;
}