#include<fstream>
using namespace std;
int n,i,j,k,a[500001],d[500001],front,back;
long long suma;
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]);
	front=1;
	back=suma=0;
	
	for(i=1;i<=n;++i)
	{
		while(front<=back&&a[i]<a[d[back]])
			--back;
		
		d[++back]=i;
		
		if(d[front]==i-k)
			++front;
		
		if(i>=k)
			suma+=a[d[front]];
	}
	printf("%ld",suma);
	return 0;
}