# 尺取り法に近い
# left, rightどこまでいけるかを毎回更新しつつ、left_idx, right_idxを動かしていく

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

start_idx = K-1
left = X[start_idx]-A[start_idx]
right = X[start_idx]+A[start_idx]
left_idx = start_idx
right_idx = start_idx
while left_idx >= 0 and right_idx <= N-1:
    improve = False
    # check left
    while left_idx-1 >= 0 and left <= X[left_idx-1] <= right:
        left = min(left, X[left_idx-1]-A[left_idx-1])
        # left をrightから更新することはないはず、なぜならA幅は同じでrightの方が遠いから
        right = max(right, X[left_idx-1]+A[left_idx-1])
        left_idx -= 1
        improve = True
    
    # check right
    while right_idx+1 <= N-1 and left <= X[right_idx+1] <= right:
        left = min(left, X[right_idx+1]-A[right_idx+1])
        right = max(right, X[right_idx+1]+A[right_idx+1])
        right_idx += 1
        improve = True
        
    #print('left', left, 'right', right, 'left_idx', left_idx, 'right_idx', right_idx)
    
    if improve == False:
        break

ans = right_idx +1 - left_idx 
print(ans)