T = gets.to_i
N = gets.to_i
C = gets.split.take(N).map(&:to_i)
V = gets.split.take(N).map(&:to_i)
CV = C.zip(V).sort_by{|c, v|}.flat_map{|c,v|
  a = []
  while v > 0
    a << [c,v]
    v /= 2
  end
  a
}

$dp = {}
def f(t, i)
  $dp[[t,i]] ||= if t == 0 || i >= CV.size
    0
  elsif t < CV[i][0]
    f(t, i + 1)
  else
    [f(t, i + 1), CV[i][1] + f(t - CV[i][0], i+1)].max
  end
end

p f(T, 0)