#include<cstdio>
int k,s,i,n,u,p,x,a[5000009];
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d%d",&n,&k,&x);
    p=1;
    u=1;
    a[1]=x;
    for(i=2;i<=n;i++)
    {
        scanf("%d",&x);
        if(a[u]<=x)
        {
            u++;
            a[u]=x;
        }
        else
        {
            while(a[u]>x&&p>=u)
            {
                u--;
            }
            a[u]=x;
        }
        if(u-p+1==k)
        {
            s=s+a[p];
            //printf("%d\n",a[p]);
            p++;
        }
    }
    printf("%d",s);
    return 0;
}