local mmi, mma = math.min, math.max
local n, x = io.read("*n", "*n")
local a = {}
for i = 1, n do
  a[i] = io.read("*n") - x
end
local b = {}
for i = 1, n do
  b[i] = io.read("*n")
end
local asum = 0
for i = 1, n do
  asum = asum + a[i]
end
if 0 <= asum then
  print(0) os.exit()
end
do
  local f = true
  for i = 1, n do
    if 0 <= a[i] then f = false break end
  end
  if f then print(-1) os.exit() end
end
asum = -asum
local t = {}
for i = 1, asum do t[i] = -1 end
for i = 1, n do
  local ai = a[i]
  local bi = b[i]
  if ai < 0 then
    ai = -ai
    for j = asum, 1, -1 do
      local dst = mmi(asum, j + ai)
      if t[dst] < 0 or t[j] + bi < t[dst] then
        t[dst] = t[j] + bi
      end
    end
    do
      local dst = mmi(asum, ai)
      if t[dst] < 0 or bi < t[dst] then
        t[dst] = bi
      end
    end
  end
end
print(t[asum])