#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

#define NMAX 10005

int cost[NMAX];
int n, k;

ll dp[NMAX];

ll solve(int i) {
	if (i >= n) {
		//printf("|-> %d\n", i);
		return 0;
	}
	if (dp[i] != -1) return dp[i];

	ll best = 1e18;

	//printf("!! %d\n", i);

	int j = i - k;
	while (j < 0) j++;
	for (; j <= i + k && j < n; j++) {
		best = min(best, solve(j + k + 1) + cost[j]);
		//printf("::%d (%d -> %d) %lld (%d)\n", j, i, j + k + 1, solve(j + k + 1) + cost[j], cost[j]);
	}

	//printf("-- %d %lld\n", i, best);
	return dp[i] = best;
}

int main() {
	while (scanf("%d %d", &n, &k) != EOF) {
		for (int i = 0; i < n; i++)
			scanf("%d", &cost[i]);

		memset(dp, -1, sizeof dp);
		printf("%lld\n", solve(0));
	}
	
	return 0;
}