from bisect import bisect_left,bisect_right
N,K = map(int,input().split())
X = list(map(int,input().split()))
A = list(map(int,input().split()))
INFTY = 2*10**17
xmax = -INFTY
xmin = INFTY
K -= 1
ind_low = K
ind_high = K
while True:
    if xmin<=X[ind_low]-A[ind_low] and xmax>=X[ind_high]+A[ind_high]:
        break
    if xmin>X[ind_low]-A[ind_low]:
        xmin = X[ind_low]-A[ind_low]
    if xmax<X[ind_high]+A[ind_high]:
        xmax = X[ind_high]+A[ind_high]
    ind_low = bisect_left(X,xmin)
    ind_high = bisect_right(X,xmax)-1
print(ind_high-ind_low+1)