#include<cstdio>
#include<deque>
#include<utility>
using namespace std;
deque<pair<int,int> > Q;
void read(),solve();
int n,k,i,a;
long long S;
int main()
{
	read();
	solve();
	return 0;
}
void read()
{
	freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	scanf("%d%d",&n,&k);
}
void solve()
{
	pair<int,int> pp;
	scanf("%d",&a);Q.push_back(make_pair(a,1));
	for(i=2;i<=n;i++)
	{
		scanf("%d",&a);
		pp=Q.back();
		for(;pp.first>a&&!Q.empty();)
		{
			Q.pop_back();
			pp=Q.back();
		}
		Q.push_back(make_pair(a,i));
		if(i>=k)
		{
			pp=Q.front();
			for(;pp.second<(i-k+1);)
			{
				Q.pop_front();
				pp=Q.front();
			}
			S+=pp.first;
		}
	}
	printf("%d",S);
}