#include<cstdio>
using namespace std;
long long j,k,s,i,n,u,p,x,b[5000009],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;
    b[1]=1;
    for(i=2;i<=n;i++)
    {
        scanf("%d",&x);
        if(a[u]<=x)
        {
            u++;
            a[u]=x;
            b[u]=i;
        }
        else
        {
            while(a[u]>x&&p<=u)
            {
                u--;
            }
            u++;
            a[u]=x;
            b[u]=i;
        }
        if(i-b[p]>=k)
        {
            p++;
        }
        if(i>=k)
            s=s+a[p];
        /*for(j=1;j<=u;j++)
        {
            printf("%d ",a[j]);
        }
        printf("  %d",p);
            printf("\n");*/
    }
    printf("%lld",s);
    return 0;
}