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