#include<cstdio>
#include<deque>
using namespace std;

int N,K,i,V[5000010];
long long int sol;
deque <int> Q;
void read(),solve();
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()
{
	for(i=1;i<=N;i++)
	{
		scanf("%d",&V[i]);
		while(!Q.empty() && V[i]<=V[Q.back()])Q.pop_back();
		Q.push_back(i);
		if(Q.front()==i-K)Q.pop_front();
		if(i>=K)
			sol+=V[Q.front()];
	}
	printf("%lld",sol);
}