N, K = map(int, input().split())
X = list(map(int, input().split()))
A = list(map(int, input().split()))

hear = {K-1}
cried = set()
while len(hear):
    h = hear.pop()
    cried.add(h)
    cdt = X[:]
    for i, c in enumerate(X):
        if X[h] - A[h] <= c <= X[h] + A[h] and i not in cried:
            hear.add(i)
            cdt.pop(0)
    X = cdt[:]
print(len(cried))