from collections import *

N, K = map(int, input().split())
inf = 10 ** 18
X = [-inf] + list(map(int, input().split())) + [inf]
A = [0] + list(map(int, input().split())) + [0]

Q = deque([K])
left = inf
right = -inf
for i in range(202020):
    s = Q[0]
    left = min(left, X[s] - A[s])
    right = max(right, X[s] + A[s])
    if X[s - 1] >= left:
        Q.appendleft(s - 1)
    b = Q[-1]
    left = min(left, X[b] - A[b])
    right = max(right, X[b] + A[b])
    if X[b + 1] <= right:
        Q.append(b + 1)
print(len(Q))