#include <cstdio>
#include <deque>

using namespace std;

const int MAX_N = 5000005;

int n,k;
int a[MAX_N];
deque<int> d;

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",&a[i]);
	long long minim=0;
	for(int i=1;i<=n;i++)
	{
		while(!d.empty() && a[i]<a[d.back()])
			d.pop_back();
		d.push_back(i);
		if(d.front() == i-k)
			d.pop_front();
		
		if(i>=k)
			minim+=a[d.front()];
	}
	printf("%lld\n",minim);
	return 0;
}