//Author: Kevin
#include<bits/stdc++.h>
//#pragma GCC optimize("O2")
using namespace std;
#define ll long long
#define ull unsigned ll
#define pb emplace_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
#define rALL(x) (x).rbegin(),(x).rend()
#define srt(x) sort(ALL(x))
#define rev(x) reverse(ALL(x))
#define rsrt(x) sort(rALL(x))
#define sz(x) (int)(x.size())
#define inf 0x3f3f3f3f
#define pii pair<int,int>
#define lb(v,x) (int)(lower_bound(ALL(v),x)-v.begin())
#define ub(v,x) (int)(upper_bound(ALL(v),x)-v.begin())
#define uni(v) v.resize(unique(ALL(v))-v.begin())
#define longer __int128_t
void die(string S){puts(S.c_str());exit(0);}
int n,m;
vector<pii> vec;
vector<int> pool;
int cnt[200200*30],ls[200200*30],rs[200200*30],tot;
ll sum[200200*30];
int rt[200200];
int build(int l,int r)
{
	int ret=++tot;
	if(l!=r)
	{
		int mid=(l+r)/2;
		ls[ret]=build(l,mid);
		rs[ret]=build(mid+1,r);
	}
	return ret;
}
int update(int x,int l,int r,int p)
{
	int ret=++tot;
	if(l==r)
	{
		cnt[ret]=cnt[x]+1;
		sum[ret]=sum[x]+pool[p];
		return ret;
	}
	int mid=(l+r)/2;
	ls[ret]=ls[x];
	rs[ret]=rs[x];
	cnt[ret]=cnt[x]+1;
	sum[ret]=sum[x]+pool[p];
	if(p<=mid)
		ls[ret]=update(ls[x],l,mid,p);
	else
		rs[ret]=update(rs[x],mid+1,r,p);
	return ret;
}
ll query(int x1,int x2,int l,int r,int c)
{
	if(!c) return 0;
	if(l==r) return (sum[x2]-sum[x1])/(cnt[x2]-cnt[x1])*c;
	int mid=(l+r)/2;
	if(cnt[rs[x2]]-cnt[rs[x1]]>=c)
		return query(rs[x1],rs[x2],mid+1,r,c);
	return query(ls[x1],ls[x2],l,mid,c-(cnt[rs[x2]]-cnt[rs[x1]]))+sum[rs[x2]]-sum[rs[x1]];
}
ll calc(int l,int r)
{
	if(r-l+1<m) return -1ll*inf*inf;
	return -2*vec[r-1].first+2*vec[l-1].first+query(rt[l-1],rt[r],0,sz(pool)-1,m);
}
ll ans=-1ll*inf*inf;
void solve(int l,int r,int L,int R)
{
	if(l>r) return ;
	int mid=(l+r)/2;
	int p=R;
	for(int i=max(L,l+m-1);i<=R;i++)
		if(calc(mid,i)>calc(mid,p))
			p=i;
	ans=max(ans,calc(mid,p));
	solve(l,mid-1,L,p);
	solve(mid+1,r,p,R);
}
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin>>n>>m;
	for(int i=0;i<n;i++)
	{
		int v,c;
		cin>>v>>c;
		pool.pb(v);
		vec.pb(c,v);
	}
	srt(vec);
	srt(pool);
	uni(pool);
	for(auto &pr:vec)
		pr.second=lb(pool,pr.second);
	rt[0]=build(0,sz(pool)-1);
	for(int i=0;i<n;i++)
		rt[i+1]=update(rt[i],0,sz(pool)-1,vec[i].second);
	solve(1,n,1,n);
	cout<<ans<<endl;
	return 0;
}