#include<stdio.h>
#include<deque>
using namespace std;

int k,s,i,j,n,m,a[5000009];
deque<int> b;

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]);
	
	for (i=1;i<=n;i++)
	{
		while (!b.empty() && a[i]<a[b.back()]) b.pop_back();
		b.push_back(i);
		if (i-b.front()==k) b.pop_front();
		if (i>=k) s+=a[b.front()];
	}
	
	printf("%d\n",s);
	return 0;
}