# K番から右と左に尺取り法
# 毎回min, maxを更新していき、それに合わせて尺取りを動かす

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


K -= 1
left = K
right = K
mn = X[K]-A[K]
mx = X[K]+A[K]
while True:
    improve = False
    
    while left > 1:
        if mn <= X[left-1]:
            left -= 1
            improve = True
            mn = min(mn, X[left]-A[left])
            mx = max(mx, X[left]+A[left])
        else:
            break            
        
    while right < N:
        if mx >= X[right+1]:
            right += 1
            improve = True
            mn = min(mn, X[right]-A[right])
            mx = max(mx, X[right]+A[right])
        else:
            break             
    #print('improve', improve, 'left', left, 'right', right)
    if improve == False:
        break
    
ans = right+1-left
print(ans)