def process(costs, k):
    # dp = [[0 for i in range(len(costs))] for j in range(k)]
    dp = [0 for i in range(len(costs) + 1)]
    for i, c in enumerate(costs):
        cmin = c
        if i - k >= 0:
            cmin += dp[i - k]
        for j in range(max(i - k, 1), i):
            if dp[j] < cmin:
                cmin = dp[j]
        dp[i + 1] = cmin
    return dp[-1]


n, k = map(int, input().split())
costs = list(map(int, input().split()))

#n, k = 3, 1
#costs = [1, 1, 1]
print(process(costs, k))