#include <stdio.h>

#define maxn 5000010
#define inf 1000000000

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 = 0, best;

	scanf("%d %d ", &N, &K);

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

	best = inf;
	for (i = 1; i <= N; i++)
	{
		if (A[i] <= best) best = A[i], p = i;

		if (p <= i-K)
		{
			best = inf, p = 0;
			for (j=0; j<K; j++)
				if (A[i-j] < best) best = A[i-j], p = i-j;
		}

		if (i >= K) Sum += best;
	}

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

	return 0;
}