#include<fstream>
#define inf 10000001
#define dim 50000000
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
long a[dim];
int i,j,k,nr;
int n;
int s;
long rez;
int p;
long minn;
long b[dim];
int main()
{
	f>>n>>k;
	for(i=1;i<=n;i++)
		f>>a[i];
	int poz=k;
	i=1;
	rez = inf;
	for (i = 1; i <= n; i++)
	{
		if (a[i] <= rez) rez = a[i], p = i;
		if (p <= i-k)
		{
			rez=inf;
			p=0;
			for (j=0; j<k; j++)
				if (a[i-j] < rez) 
					{
						rez=a[i-j];
						p=i-j;
				}
		}
		if (i>=k) 
			s+=rez;
	}
	g<<s;
}