#include <stdio.h>

#define maxn 5000010
#define inf 2000000000

int n, k;
int a[maxn];
long long sum;

int main()
{
	freopen("deque.in", "r", stdin);
	freopen("deque.out", "w", stdout);

	int i, j, p, best;

	scanf("%d %d ", &n, &k);

	for (i = 1; i <= n; i++) scanf("%d ", &a[i]);

	best = inf, p = n+1;

	for (i=n; i>0; i--)
	{
		if (a[i] <= best) best = a[i], p = i;

		if (p >= i+k)
		{
			best = inf, p = n+1;

			for (j=0; j<k; j++)
				if (a[i+j] < best) best = a[i+j], p = i+j;
		}

		if (i <= n-k+1) sum += best;
	}

	printf("%lld\n", sum);

	return 0;
}