import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N,K = map(int,readline().split())
X = tuple(map(int,readline().split()))
A = tuple(map(int,readline().split()))

INF = 10 ** 18

X = (-INF,) + X + (INF,)
A = (-INF,) + A + (INF,)

L = X[K] - A[K]
R = X[K] + A[K]
answer = 1

def add_frog(n):
    global L, R, answer
    L = min(L, X[n] - A[n])
    R = max(R, X[n] + A[n])

l = r = K
while True:
    if X[l-1] >= L:
        l -= 1
        add_frog(l)
        continue
    if X[r+1] <= R:
        r += 1
        add_frog(r)
        continue
    break

answer = r - l + 1
print(answer)