# leftに行けるだけ行く、rightにも行けるだけ行く、両側のマックスを両サイドから更新
# をwhile Trueで繰り返す

N, K = map(int, input().split())
X = list(map(int, input().split()))
A = list(map(int, input().split()))

left_idx = K-1
right_idx = K-1
left_min = X[left_idx]-A[left_idx]
right_max = X[right_idx]+A[right_idx]

while 0 <= left_idx and right_idx < N:
    update = False
    
    # go left
    while left_idx-1 >= 0 and left_min <= X[left_idx-1]:
        left_idx -= 1
        update = True
        left_min = min(left_min, X[left_idx]-A[left_idx])
        right_max = max(right_max, X[left_idx]+A[left_idx])
    
    # go right
    while right_idx+1 < N and X[right_idx+1] <= right_max:
        right_idx += 1
        update = True
        left_min = min(left_min, X[right_idx]-A[right_idx])
        right_max = max(right_max, X[right_idx]+A[right_idx])
    
    #print('update', update, 'left_idx', left_idx, 'right_idx', right_idx, 'left_min', left_min, 'right_max', right_max)
    if update == False:
        break

ans = right_idx - left_idx + 1
print(ans)