n,k = map(int,input().split())
A = list(map(int,input().split()))
k -= 1
if A[k]==0:
    print(0)
else:
    
    l,r = k+1, k-1
    for r in range(k+1, n):
        if A[r]==0 or A[r]%2!=0:
            break
    
    for l in range(k-1, 0, -1):
        if A[l]==0 or A[l]%2!=0:
            break
    
    sr = sum(A[k+1:r+1])
    sl = sum(A[l:k])
    
    if A[k]==1:
        print(A[k] + max(sr, sl))
    else:
        print(A[k] + sr + sl)