#include<stdio.h>
#define N 5000010
int n,k,a[N],d[N];
long long rez;
int main()
{
	freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	int p=1,u=0;
	scanf("%d%d",&n,&k);
	for(int i=1; i<=n; i++)
	{
		scanf("%d",&a[i]);
		while(p<=u && i-d[p]>=k)
			p++;
		while(p<=u && a[i]<=a[d[u]])
			u--;
		d[++u]=i;
		if(i>=k)
			rez+=(long long)a[d[p]];
	}
	printf("%lld\n",rez);
	return 0;
}