import sys

sys.setrecursionlimit(10**6)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.buffer.readline())
def LI(): return list(map(int, sys.stdin.buffer.readline().split()))
def LI1(): return list(map(int1, sys.stdin.buffer.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def BI(): return sys.stdin.buffer.readline().rstrip()
def SI(): return sys.stdin.buffer.readline().rstrip().decode()
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
inf = 10**16
md = 998244353
# md = 10**9+7

n,k=LI()
xx=LI()
aa=LI()

k-=1
i=j=k

l=xx[k]-aa[k]
r=xx[k]+aa[k]
update=True
while update:
    update=False
    while i-1>=0 and xx[i-1]>=l:
        i-=1
        l=min(l,xx[i]-aa[i])
        r=max(r,xx[i]+aa[i])
        update=True
    while j+1<n and xx[j+1]<=r:
        j+=1
        l=min(l,xx[j]-aa[j])
        r=max(r,xx[j]+aa[j])
        update=True

print(j-i+1)