import bisect

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

r = [0]*n    
r[k-1] = 1

L = [X[k-1]-A[k-1]]
R = [X[k-1]+A[k-1]]
lprev = n-1
rprev = -1
left = 0
right = n-1
while not (lprev <= left and right <= rprev):
    left = bisect.bisect_left(X,min(L))
    right = bisect.bisect_right(X,max(R))-bisect.bisect_right(X,min(L))
    L = []
    R = []
    for i in range(left,min(n,right+1)):
        r[i] = 1
        L.append(X[i]-A[i])
        R.append(X[i]+A[i])
    lprev = left
    rprev = right

print(sum(r))