'''input
6 2
20 10 5 1 3 4
'''

def rints():
    return list(map(int, input().split()))

def ri():
    return int(input())



def solve(n, k, c):
    used = [-1] * n
    dp = [10**15 + 2] * n
    for i in range(n):
        used[i] = c[i]
        if i > k:
            used[i] += dp[i-k-1]
        # dp[i] = used[i]
        for j in range(i-k, i+k+1):
            if j < 0 or j > n-1 or i == j:
                continue
            dp[i] = min(dp[i], used[i])
            if j < i:
                dp[i] = min(dp[i], used[j])
            elif j > i:
                dp[i] = min(dp[i], c[j] + (dp[j-k-1] if (j-k-1) >= 0 else 0))
    return dp[n-1]
    
def main():
    n, k = rints()
    costs = rints()
    print(solve(n, k, costs))

main()