#include<bits/stdc++.h>
#define int long long
using namespace std;
struct segment1
{
	int tr[800005];
	void change(int k,int l,int r,int x,int v)
	{
		if(l==r){tr[k]=v;return;}
		int mid=(l+r)>>1;
		if(x<=mid)change(k<<1,l,mid,x,v);
		else change(k<<1|1,mid+1,r,x,v);
		tr[k]=min(tr[k<<1],tr[k<<1|1]);
	}
	int query(int k,int l,int r,int x,int y)
	{
		if(x>y)return 0x3f3f3f3f;
		if(x<=l&&r<=y)return tr[k];
		int mid=(l+r)>>1,res=0x3f3f3f3f;
		if(x<=mid)res=min(res,query(k<<1,l,mid,x,y));
		if(y>mid)res=min(res,query(k<<1|1,mid+1,r,x,y));
		return res;
	}
	int find(int k,int l,int r,int x)
	{
		if(tr[k]>=x)return -1;
		if(l==r)return l;
		int mid=(l+r)>>1;
		if(tr[k<<1]<x)return find(k<<1,l,mid,x);
		else return find(k<<1|1,mid+1,r,x);
	}
}sg1;
struct point{int l,r,w;};set<point>s;
bool operator <(point x,point y)
{
	if(x.w!=y.w)return x.w<y.w;
	return x.l<y.l;
}
struct point2{int l,r,w;};set<point2>s2;
int n,a[200005],sum[200005],k,f[200005],cnt;
bool operator <(point2 x,point2 y)
{
	if(x.r!=y.r)return x.r<y.r;
	return x.l<y.l;
}
struct segment2
{
	struct tree{int l,r,id;}tr[6000005];
	struct line
	{
		int k,b;
		int calc(int x){return k*x+b;}
	}w[1000005];
	int rt[800005],tot;
	void insert(int &k,int l,int r,int x)
	{
		if(!k){tr[k=++tot].id=x;return;}
		int mid=(l+r)>>1;
		if(w[x].calc(mid)>w[tr[k].id].calc(mid))swap(x,tr[k].id);
		if(l==r)return;
		if(w[x].calc(l)>w[tr[k].id].calc(l))insert(tr[k].l,l,mid,x);
		if(w[x].calc(r)>w[tr[k].id].calc(r))insert(tr[k].r,mid+1,r,x);
	}
	int query(int k,int l,int r,int x)
	{
		if(!k)return -0x3f3f3f3f3f3f3f3f;
		int res=w[tr[k].id].calc(x),mid=(l+r)>>1;
		if(x<=mid)res=max(res,query(tr[k].l,l,mid,x));
		else res=max(res,query(tr[k].r,mid+1,r,x));
		return res; 
	}
	void change(int k,int l,int r,int x)
	{
		insert(rt[k],1,n,x);
		if(l==r)return;
		int mid=(l+r)>>1;
		if(x<=mid)change(k<<1,l,mid,x);
		else change(k<<1|1,mid+1,r,x);
	}
	int query(int k,int l,int r,int x,int y,int w)
	{
		if(x<=l&&r<=y)return query(rt[k],1,n,w);
		int mid=(l+r)>>1,res=-0x3f3f3f3f3f3f3f3f;
		if(x<=mid)res=max(res,query(k<<1,l,mid,x,y,w));
		if(y>mid)res=max(res,query(k<<1|1,mid+1,r,x,y,w));
		return res;
	}
}sg2;
struct segment3
{
	struct tree{int l,r,id;}tr[6000005];
	struct line
	{
		int k,b;
		int calc(int x){return k*x+b;}
	}w[1000005];
	const int V=4e10;
	int tot,rt[800005];
	void insert(int &k,int l,int r,int x)
	{
		if(!k){tr[k=++tot].id=x;return;}
		int mid=(l+r)>>1;
		if(w[x].calc(mid)>w[tr[k].id].calc(mid))swap(x,tr[k].id);
		if(l==r)return;
		if(w[x].calc(l)>w[tr[k].id].calc(l))insert(tr[k].l,l,mid,x);
		if(w[x].calc(r)>w[tr[k].id].calc(r))insert(tr[k].r,mid+1,r,x);
	}
	int query(int k,int l,int r,int x)
	{
		if(!k)return -0x3f3f3f3f3f3f3f3f;
		int res=w[tr[k].id].calc(x),mid=(l+r)>>1;
		if(x<=mid)res=max(res,query(tr[k].l,l,mid,x));
		else res=max(res,query(tr[k].r,mid+1,r,x));
		return res; 
	}
	void change(int k,int l,int r,int x,int w)
	{
		insert(rt[k],1,V,w);
		if(l==r)return;
		int mid=(l+r)>>1;
		if(x<=mid)change(k<<1,l,mid,x,w);
		else change(k<<1|1,mid+1,r,x,w);
	}
	int query(int k,int l,int r,int x,int y,int w)
	{
		if(x<=l&&r<=y)return query(rt[k],1,V,w);
		int mid=(l+r)>>1,res=-0x3f3f3f3f3f3f3f3f;
		if(x<=mid)res=max(res,query(k<<1,l,mid,x,y,w));
		if(y>mid)res=max(res,query(k<<1|1,mid+1,r,x,y,w));
		return res;
	}
}sg3;
signed main()
{
	//cin.tie(0)->sync_with_stdio(0);
	cin>>n>>k;
	for(int i=1;i<=n;i++)cin>>a[i],sum[i]=sum[i-1]+a[i];
	f[0]=0;sg2.w[1]={-sum[0],f[0]};sg2.change(1,1,n,1);
	for(int i=1;i<=n;i++)
	{
		int now=(a[i]==0?1:0);
		if(!s.size())
		{
			s.insert(point{i,i,now});s2.insert(point2{i,i,now});
			sg3.w[++cnt]={now,sg2.query(1,1,n,i,i,now)};
			sg3.change(1,1,n,i,cnt);
		}
		else 
		{
			auto ed=s.begin();int l=ed->l,r=ed->r,w=ed->w;
			if(w==now)
			{
				s.erase(*ed),s.insert(point{l,i,w});
				s2.erase(s2.find(point2{l,r,w}));s2.insert(point2{l,i,w});
				sg3.w[++cnt]={w,sg2.query(1,1,n,l,i,w)};
				sg3.change(1,1,n,l,cnt);
			}
			else 
			{
				s.insert(point{i,i,now});s2.insert(point2{i,i,now});
				sg3.w[++cnt]={now,sg2.query(1,1,n,i,i,now)};
				sg3.change(1,1,n,i,cnt);
			}
		}
		sg1.change(1,0,n,a[i],i);
		auto it=s.lower_bound(point{0,0,a[i]});
		if(it->w==a[i])
		{
			int l=it->l,r=it->r;s.erase(it);s2.erase(s2.find({l,r,it->w}));
			while(l<=r)
			{
				int w=sg1.find(1,0,n,r);
				int p=max(l,sg1.query(1,0,n,0,w)+1);
				s.insert(point{p,r,w});s2.insert(point2{p,r,w});
				sg3.w[++cnt]={w,sg2.query(1,1,n,p,r,w)};
				sg3.change(1,1,n,p,cnt);
				r=p-1;
			}
		}
		//cout<<i<<'\n';
		f[i]=sg3.query(1,1,n,max(1ll,i-k+1),i,sum[i]);
		auto it2=s2.lower_bound({0,i-k+1,0});
		f[i]=max(f[i],sg2.query(1,1,n,i-k+1,it2->r,it2->w)+sum[i]*it2->w);
		if(i<n)sg2.w[i+1]={-sum[i],f[i]},sg2.change(1,1,n,i+1);
		//cout<<i<<'\n';
		//for(auto it=s.begin();it!=s.end();it++)cout<<it->l<<' '<<it->r<<' '<<it->w<<'\n';
	}
	cout<<f[n];
	return 0;
}