N,X = map(int,input().split())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
import sys
flag = False
for a in A:
    if a >= X:
        flag = True
        break
if not flag:
    print(-1)
    exit()
now = 0
C = []
D = []
for i in range(N):
    now += A[i] - X
    if A[i] < X:
        C.append(X-A[i])
        D.append(B[i])
if now >= 0:
    print(0)
    exit()
now = -now
inf = 10 ** 8
N = len(D)
dp = [[inf] * (now+1) for _ in range(N)]
A = C
B = D
dp[0][min(now,A[0])] = B[0]
dp[0][0] = 0
for i in range(N-1):
    for j in range(now+1):
        dp[i+1][j] = min(dp[i+1][j],dp[i][j])
        dp[i+1][min(now,j+A[i+1])] = min(dp[i+1][min(now,j+A[i+1])],dp[i][j] + B[i+1])
print(dp[-1][-1])