n, x = [int(i) for i in input().split()]
a = [int(i)-x for i in input().split()]
b = [int(i) for i in input().split()]


if all(map(lambda x: x < 0, a)):
    print(-1)
    exit()

sum_a = sum(a)
if sum_a >= 0:
    print(0)
    exit()
sum_a *= -1

dp = [10 ** 8] * (sum_a+1)
dp[0] = 0

for index, score in enumerate(a):
    if score >= 0:
        continue

    for i in reversed(range(sum_a)):
        j = min(sum_a, i - score)
        dp[j] = min(dp[j], dp[i] + b[index])

print(dp[-1])