#include<cstdio>
#include<queue>
#include<algorithm>
#define x first
#define y second
using namespace std;

deque< pair<int,int> > q;
pair<int, int> aux;
int n,k,s;
int main()
{
	freopen("deque.in","rt",stdin);
	freopen("deque.out","wt",stdout);
	scanf("%d%d",&n,&k);
	for(int i=1;i<=n;i++)
	{
		scanf("%d",&aux.x);
		aux.y=i;
		while(q.size()) 
			if(aux.x < q.back().x) q.pop_back();
			else break;
		q.push_back( aux );
		if(q.front().y <= i-k) q.pop_front();
		if(i>=k) s+=q.front().x;
	}
	printf("%d\n",s);
	return 0;
}