# しゃくとり法に近い、two pointer、left_min, right_max, left_idx, right_idxを管理してwhile使う

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

K -= 1
left_idx = K
right_idx = K
left_min = X[K]-A[K]
right_max = X[K]+A[K]
#print('left_idx', left_idx, 'right_idx', right_idx, 'left_min', left_min, 'right_max', right_max)
while left_idx>0 or right_idx<N-1:
    improve = False
    
    while left_idx-1>=0 and left_min <= X[left_idx-1] <= right_max:
        improve = True
        left_idx -= 1
        left_min = min(left_min, X[left_idx]-A[left_idx])
        right_max = max(right_max, X[left_idx]+A[left_idx])

    while right_idx+1<=N-1 and left_min <= X[right_idx+1] <= right_max:
        improve = True
        right_idx += 1
        left_min = min(left_min, X[right_idx]-A[right_idx])
        right_max = max(right_max, X[right_idx]+A[right_idx])      

    #print('left_idx', left_idx, 'right_idx', right_idx, 'left_min', left_min, 'right_max', right_max, 'improve', improve)
    if improve == False:
        break

#print('left_idx', left_idx, 'right_idx', right_idx)
ans = right_idx+1-left_idx
print(ans)