N, X = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
C, D = [], []
V = 0
for i in range(N):
    if A[i] - X < 0:
        C.append(X - A[i])
        D.append(B[i])
    V += A[i] - X

if V >= 0:
    print(0)
    exit()

V = -V
S = sum(C)
inf = 10 ** 18
pre = [inf] * (S + 1)
pre[0] = 0
for i in range(len(C)):
    dp = [inf] * (S + 1)
    for j in range(S + 1):
        dp[j] = pre[j]
        if j - C[i] >= 0:
            dp[j] = min(dp[j], dp[j - C[i]] + D[i])
    dp, pre = pre, dp

ans = inf
for i in range(V, S + 1):
    ans = min(ans, pre[i])

print(ans) if ans != sum(B) else print(-1)