N, K = [int(i) for i in input().split()]
X = [int(i) for i in input().split()]
A = [int(i) for i in input().split()]

left = right = K - 1

lower = X[left] - A[left]
upper = X[right] + A[right]

ans = -1
while ans != right - left:
    ans = right - left
    while 0 < left and lower <= X[left - 1]:
        left -= 1
        upper = max(upper, X[left] + A[left])
        lower = min(lower, X[left] - A[left])
    while right < N - 1 and X[right + 1] <= upper:
        right += 1
        upper = max(upper, X[right] + A[right])
        lower = min(lower, X[right] - A[right])

print(ans + 1)