from copy import *
n,k=map(int, input().split())
c=list(map(int, input().split()))
C=[]
for i in range(n):
    a=c[i];j=i;cost=0
    b=copy(c)
    while set(b)!={0} and j<n:
        lo=j-k;up=j+k+1
        if j-k<0 :
            lo=0
        if up>n-1:
            up=n-1
        if b[j]!=0 :
            cost+=c[j]            
        b[lo:up]=[0 for i in b[lo:up]]  
        C.append(cost)
        j+=1
print(min(C))