#include <cstdio>
#include <queue>

using namespace std;
typedef pair<int,int> ii;
deque <ii> q;
int main()
{
	freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	int n,k,i,x,s=0;
	scanf("%d%d",&n,&k);
	for(i=1;i<=n;++i)
	{
		scanf("%d",&x);
		while(!q.empty() && q.back().first>=x)
		{
			q.pop_back();
		}
		q.push_back(ii(x,i));
		if(i>=k)
		{
			while(!q.empty() && i-q.front().second+1>k)
				q.pop_front();
			s=s+q.front().first;
		}
	}
	printf("%d\n",s);
	return 0;
}