#exec({'RUBY_THREAD_VM_STACK_SIZE'=>'100000000'},'/usr/bin/ruby', $0) if !ENV['RUBY_THREAD_VM_STACK_SIZE']

def inpf() a=gets.chomp.split(" ").map(&:to_f)end

def inps() a=gets.chomp.split(" ")end

def copy(a) Marshal.load(Marshal.dump(a)) end

def kaijo(n,r = 10**9+7)(n < 2)? 1 : (2..n).inject{|memo,u|memo=(memo*u)%r} end

def na(n,d=0) Array.new(n,d)end

def na2(n,m,d=0) Array.new(n){Array.new(m,d)}end

def na3(n,m,l,d=0) Array.new(n){Array.new(m){Array.new(l,d)}}end

def inp() a=gets.chomp.split(" ").map(&:to_i)end

def r_up(a, b) (a+b-1)/b end

def sum(a) a.inject(:+) end

def b_ser(l,r)
  mid = (r+l)/2
  if(mid == l)
    return (j(mid))? mid : mid+1 
  end
  if(j(mid))
    b_ser(l,mid)
  else
    b_ser(mid,r)
  end
end
def j(d)
  c = @k
  @n.times do |i|
    sa = @a[i]* @b[i] - d
    if(sa > 0)
      c -= r_up(sa,@b[i])
    end
    return false if(c < 0)
  end
  return true
end
@n,@k = inp

@a = inp.sort
@b = inp.sort.reverse

p b_ser(0,10**12)
