n, x = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))

inf = 1 << 60
dp = [[-inf] * (100 * n + 1) for _ in range(n + 1)]
dp[0][0] = 0
for i, (a, b) in enumerate(zip(A, B), 1):
    for j in range(i, 0, -1):
        for k in range(100 * j, a - 1, -1):
            dp[j][k] = max(dp[j][k], dp[j - 1][k - a] + b)

ans = -inf
for i in range(1, n + 1):
    for j in range(x * i, 100 * i + 1):
        ans = max(ans, dp[i][j])

if ans < 0:
    print(-1)
else:
    print(sum(B) - ans)