#include <cstdio>
#include <deque>

using namespace std;

deque<int> dq;
int v[5000001] , n , k;
long long sum;

int main()
{
	freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	scanf("%d %d",&n,&k);
	for(int i=1;i<=n;++i)
	{
		scanf("%d",&v[i]);
		while(!dq.empty() && v[i]<=v[dq.back()]) dq.pop_back();
		dq.push_back(i);
		if(dq.front()==i-k) dq.pop_front();
		if(i>=k) sum+=v[dq.front()];
	}
	printf("%lld\n",sum);
	return 0;
}