N,K = map(int,input().split())
X = list(map(int,input().split()))
A = list(map(int,input().split()))
kukan = [X[K-1]-A[K-1], X[K-1]+A[K-1]]
l = r = K
flg = True
while flg:
  flg = False
  while kukan[0] <= X[l-1] <= kukan[1] and l >= 2:
    l-=1
    kukan[0] = min(kukan[0], X[l-1]-A[l-1])
    kukan[1] = max(kukan[1], X[l-1]+A[l-1])
    flg = True
    while kukan[0] <= X[r+1] <= kukan[1] and r <= N-3:
      r+=1
      kukan[0] = min(kukan[0], X[r+1]-A[r+1])
      kukan[1] = max(kukan[1], X[r+1]+A[r+1])
      flg = True
print(r-l+1)