N = gets.to_i
L = gets.split.map(&:to_i)
K = gets.to_i

def f(x)
  cnt = 0

  L.each do |l|
    cnt += Rational(l, x).floor
  end

  K <= cnt
end

ok = 0.0
ng = 10.0 ** 18

100.times do
  x = (ok + ng) / 2.0

  if f(x)
    ok = x
  else
    ng = x
  end
end

puts ok.round(12)