INF = 1 << 60

n, x = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))

for i in range(n):
  a[i] -= x

if all([x < 0 for x in a]):
  print("-1")
  exit()

cost = - sum(a)
if cost <= 0:
  print("0")
  exit()

dp = {}
dp[0] = 0
ans = INF
for i in range(n):
  if a[i] >= 0:
    continue

  ndp = {}
  for k, v in dp.items():
    ndp[k] = min(ndp.get(k, INF), v)
    nxt = k - a[i]
    if nxt >= cost:
      ans = min(ans, v + b[i])
    else:
      ndp[nxt] = min(ndp.get(nxt, INF), v + b[i])

  dp = ndp

print(ans)