#include <stdio.h>

using namespace std;

int v[5000005];
int deq[5000005];

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    int n,k,i,p,u,a,poz,len,m=-1000000,deltapoz,pozfin;
    scanf("%d%d",&n,&k);
    for(i=1;i<=n;i++)
        scanf("%d",v+i);

    p=1;u=0;
    //pt deque
    int sum=0;
/*
    for(i=1;i<=k;i++)
    {
        a=v[i];
        while(p<=u&&v[deq[u]]>a)
            u--;
        deq[++u]=i;
    }

    for(i=k+1;i<=n;i++)
    {
        a=v[i];
        while(p<=u&&v[deq[u]]>a)
            u--;
        deq[++u]=i;
        if(i-deq[p]>=k) p++;
        if(m<v[deq[p]])
        {
            m=v[deq[p]];
            poz=deq[p]; // i sau deq[p]
        }
    }

    for(i=poz-1;v[i]>m;i--);

    deltapoz=poz-i;
    if(k<deltapoz) pozfin=poz;
    else pozfin=poz+k-deltapoz;
    printf("%d %d %d",i+1,pozfin,m);
    //printf("%d %d %d",poz-k+1,poz,m);
*/

    for(i=1;i<=k;i++)
    {
        a=v[i];
        while(p<=u&&v[deq[u]]>a)
            u--;
        deq[++u]=i;

    }
    sum+=v[deq[p]];
    for(i=k+1;i<=n;i++)
    {
        a=v[i];
        while(p<=u&&v[deq[u]]>a)
            u--;
        deq[++u]=i;
        if(i-deq[p]>=k) p++;
        sum+=v[deq[p]];
    }
    printf("%d",sum);
    return 0;
}