# Enter your code here. Read input from STDIN. Print output to STDOUT

def solve(c, k, i = 0, cache = [])  
    return 0 if i >= c.size
    return cache[i] if cache[i]
    prices = []
    0.upto (k) do |j|
        return 0 if i + j >= c.size
        prices << (c[i + j] + solve(c, k, i + j + 1, cache))
    end
    r = prices.min
    cache[i] = r
    r
end

n, k = gets.split(' ').map(&:to_i)
c = gets.split(' ').map(&:to_i)
if k == 0
    p c.reduce(:+)
elsif k >= n
    p c.min
else
    p solve(c, k)    
end