N,K = map(int,input().split())
X = list(map(int,input().split()))
A = list(map(int,input().split()))
check = [0]*N
kukan = [X[K-1]-A[K-1], X[K-1]+A[K-1]]
flg = True
while flg:
  count = 0
  for i in range(N):
    if kukan[0] <= X[i] <= kukan[1] and check[i] == 0:
      check[i] = 1
      count += 1
      kukan[0] = min(kukan[0], X[i]-A[i])
      kukan[1] = max(kukan[1], X[i]+A[i])
  if count == 0 or sum(check) == N:
    flg = False
print(sum(check))