# include <bits/stdc++.h>
using namespace std;
using ll=long long;
constexpr ll INF=1e18;
int m,X[200010],N=0;
ll ans=-INF;
struct Node
{
	int v,c;
	bool operator<(const Node &t)const{return c<t.c;}
}a[200010];
namespace S
{
	int rt[200010],lc[4000010],rc[4000010],cnt[4000010],tot=0;
	ll sum[4000010];
	inline void pushup(int rt)
	{
		cnt[rt]=cnt[lc[rt]]+cnt[rc[rt]];
		sum[rt]=sum[lc[rt]]+sum[rc[rt]];
	}
	void update(int &rt,int l,int r,int x)
	{
		lc[++tot]=lc[rt];rc[tot]=rc[rt];cnt[tot]=cnt[rt];sum[tot]=sum[rt];rt=tot;
		if(l==r) return cnt[rt]++,sum[rt]+=X[x],void();
		int mid=(l+r)/2;
		if(x<=mid) update(lc[rt],l,mid,x);
		else update(rc[rt],mid+1,r,x);
		pushup(rt);
	}
	ll query(int r1,int r2,int l,int r,int x)
	{
		if(l==r) return assert(x<=cnt[r1]-cnt[r2]),(ll)min(x,cnt[r1]-cnt[r2])*X[l];
		int mid=(l+r)/2;
		if(x<=cnt[rc[r1]]-cnt[rc[r2]]) return query(rc[r1],rc[r2],mid+1,r,x);
		else return sum[rc[r1]]-sum[rc[r2]]+query(lc[r1],lc[r2],l,mid,x-(cnt[rc[r1]]-cnt[rc[r2]]));
	}
	inline ll query(int l,int r,int x){assert(x<=cnt[rt[r]]-cnt[rt[l-1]]);return query(rt[r],rt[l-1],1,N,x);}
}
inline void chkmax(ll &x,const ll &y){x=max(x,y);}
void slv(int l,int r,int L,int R)
{
	if(l>r) return;
	int mid=(l+r)/2,M;
	ll maxn=-INF;
	for(int i=L;i<=R && i<=mid-m+1;i++)
	{
		ll s=S::query(i+1,mid-1,m-2)+a[i].v+a[mid].v-2*(a[mid].c-a[i].c);
		if(s>maxn) M=i,maxn=s;
	}
	chkmax(ans,maxn);
	slv(l,mid-1,L,M);slv(mid+1,r,M,R);
}
int main()
{
	int n;
	cin>>n>>m;
	for(int i=1;i<=n;i++) scanf("%d%d",&a[i].v,&a[i].c),X[++N]=a[i].v;
	sort(a+1,a+n+1);
	sort(X+1,X+N+1);
	N=unique(X+1,X+N+1)-X-1;
	auto get=[](int x){return lower_bound(X+1,X+N+1,x)-X;};
	for(int i=1;i<=n;i++) S::update(S::rt[i]=S::rt[i-1],1,N,get(a[i].v));
	slv(1,n,1,n);
	cout<<ans<<endl;
	return 0;
}