#input of int(split by space)
def get_i()
  return gets.chomp.split(" ").map(&:to_i)
end
#input of float(split by space)
def get_f()
  return gets.chomp.split(" ").map(&:to_f)
end
#input of string(split by space)
def get()
  return gets.chomp.split(" ")
end
#input of string(split per one character)
def get_nsp()
  return gets.chomp.split("")
end
#yes or no decision
def yn_judge(bool,y="Yes",n="No")
  return bool ? y : n 
end
#create of array
def array(size1,init=nil,size2=-1)
  if size2==-1
      return Array.new(size1){init}
  else
      return Array.new(size2){Array.new(size1){init}}
  end
end

def max(a,b)
    return a>b ? a : b
end

def min(a,b)
    return a>b ? b : a
end

INF=Float::INFINITY

N,K=get_i
A=get_i.sort{|x,y| y<=>x}
F=get_i.sort
def fulfil?(x)
    res=0
    N.times do|i|
      res+=A[i]-x/F[i]
    end
    return res<=K
end
head=-1
tail=A[0]*F[-1]+1
while tail-head>1
  mid=head+(tail-head)/2
  if fulfil?(mid)
      tail=mid
  else
      head=mid
  end
end
puts tail