#include <cstdio>
int n,k,i,p,u,a[5000005],x[5000005];
long long s;
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d",&n,&k);
    for(i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
    }
    p=1;
    for(i=1;i<=n;i++)
    {
        while(p<=u&&a[x[u]]>a[i])
            u--;
        u++;
        x[u]=i;
        if(i-k==x[p])p++;
        if(i>=k)s=s+a[x[p]];
    }
    printf("%lld",s);
    return 0;
}