n, k = map(int, input().split())
X = list(map(int, input().split()))
A = list(map(int, input().split()))

X.sort()

k -= 1

l = k
r = k
ld = X[k]-A[k]
rd = X[k]+A[k]

flag = True
while flag:
    flag = False
    while l-1 >= 0 and ld <= X[l-1]:
        flag = True
        l -= 1
        ld = min(ld, X[l]-A[l])
        rd = max(rd, X[l]+A[l])
    while r+1 <= n-1 and X[r+1] <= rd:
        flag = True
        r += 1
        rd = max(rd, X[r]+A[r])
        ld = min(ld, X[r]+A[r])
print(r-l+1)