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

hear = [K-1]
cried = []
while len(hear):
    h = hear.pop()
    cried.append(h)
    for i, c in enumerate(X):
        if X[h] - A[h] <= c <= X[h] + A[h] and i not in cried:
            hear.append(i)
print(len(cried))