#include<cstdio>
#include<cstring>
#include<algorithm>
#define LL long long
#define inf 99999999999999LL
using namespace std;
const int M=100007;
int read(){
    int ans=0,f=1,c=getchar();
    while(c<‘0‘||c>‘9‘){if(c==‘-‘) f=-1; c=getchar();}
    while(c>=‘0‘&&c<=‘9‘){ans=ans*10+(c-‘0‘); c=getchar();}
    return ans*f;
}
LL ans,mn=inf,f[M];
int w[M],head,tail,k,n;
struct node{int pos; LL v;}q[M];f
int main()
{
    n=read(); k=read();
    for(int i=1;i<=n;i++) w[i]=read(),ans+=w[i];
    for(int i=1;i<=n;i++){
        f[i]=q[head].v+w[i];
        while(head<=tail&&q[tail].v>f[i]) tail--;
        q[++tail].v=f[i]; q[tail].pos=i;
        while(head<=tail&&q[head].pos<i-k) head++;
    }
    for(int i=n-k;i<=n;i++) mn=min(mn,f[i]);
    printf("%lld\n",ans-mn);
    return 0;
}