import sys

# sys.setrecursionlimit(200005)
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, x = LI()
aa = LI()
bb = LI()
aa = [-a+x for a in aa]
s = sum(aa)
if s <= 0:
    print(0)
    exit()

dp = [inf]*(s+1)
dp[0] = 0
for a, b in zip(aa, bb):
    if a <= 0: continue
    for i in range(s, -1, -1):
        pre = dp[i]
        if pre == inf: continue
        ni = min(i+a, s)
        dp[ni] = min(dp[ni], pre+b)

ans = dp[-1]
if ans >= sum(bb): ans = -1

print(ans)