import sys

sys.setrecursionlimit(200005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

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 = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

class Bit:
    def __init__(self, op, e, n):
        self.op = op
        self.e = e
        self.n = n+1
        self.table = [e() for _ in range(self.n)]

    def update(self, i, x):
        i += 1
        while i < self.n:
            self.table[i] = self.op(self.table[i], x)
            i += i & -i

    # [0,i]
    def prod(self, i):
        i += 1
        res = self.e()
        while i > 0:
            res = self.op(res,self.table[i])
            i -= i & -i
        return res

from collections import defaultdict

# left
# u-u1<=(t-t1)*k
# u-u1<=kt-kt1
# kt1-u1<=kt-u

# right
# u1-u<=(t-t1)*k
# u1-u<=kt-kt1
# kt1+u1<=kt+u

n,k=LI()
tt=LI()
xx=LI()
cc=LI()

enc=set()
for t,x in zip(tt,xx):enc.add(k*t+x)
enc.add(0)
enc={a:i for i,a in enumerate(sorted(enc))}
m=len(enc)
bit=Bit(max,lambda :-inf,m+5)
bit.update(enc[0],0)

for i in sorted(range(n),key=lambda i:k*tt[i]-xx[i]):
    t,x=tt[i],xx[i]
    if k*t-x<0:continue
    p=enc[k*t+x]
    mx=bit.prod(p)
    if mx==-inf:continue
    bit.update(p,mx+cc[i])

print(bit.prod(m))