def loco(l,k):
    if len(l)<= k-1:return 0
    kaka = l[0]+loco(l[1:],k)
    for i in range(1,k):
        kaka = min(kaka, l[i] + loco(l[i+1:],k))
    return kaka
print(loco([20,30,40,25,15,20,28],3))