n, x = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
ab = [(a, b) for a, b in zip(A, B)]
ab.sort(reverse = True)
ans = 0
tot = 0
lst = []
for a, b in ab:
    if a >= x:
        ans += b
        tot += a - x
    else:
        lst.append((x - a, b))
if ans == 0:
    print(-1)
    exit()
dp = [0] * (tot + 1)
for a, b in lst:
    for i in range(tot, a - 1, -1):
        dp[i] = max(dp[i], dp[i - a] + b)
ans += dp[-1]
print(sum(B) - ans)