#include<cstdio>
#include<queue>
using namespace std;
int v[5000005]; 
typedef pair<int,int> ii;
deque <ii>q;
int main()
{
	freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	int n,k,i;
	long long s=0;
	scanf("%d%d",&n,&k);
	for(i=1; i<=n; i++)
		scanf("%d",&v[i]);
	for(i=1; i<=n; i++)
	{
		while(!q.empty() && q.back().first>=v[i])
			q.pop_back();
		q.push_back(ii(v[i],i));
		while(!q.empty() && i-q.front().second+1>k)
			q.pop_front();
		if(i>=k)
			s=s+q.front().first;
	}
	printf("%lld\n",s);
	return 0;
}