N, K = [ int(a) for a in input().split(' ') ]
alist = [ int(a) for a in input().split(' ') ]

agenda = []
enumed = list(enumerate(alist))
for num_subl in range(1,N//K+1):
    taken = set()
    isum = 0
    prev = -1
    for i in range(num_subl):
        start = max(prev+1, K*(i+1)-1)
        end = start+(num_subl-i-1)*(K-1)+ (N-num_subl*K if i > 0 else 0)
        ind, val = min(enumed[start:end+1], key=lambda p:p[1] if p[0] not in taken else float("inf"))
        taken.add(ind)
        isum += val
        prev = ind
    agenda.append(isum)
print(min(agenda))