#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;
}