local t, n = io.read("*n", "*n")
local cs = {}
local vs = {}
for i = 1, n do
  cs[i] = io.read("*n")
end
for i = 1, n do
  vs[i] = io.read("*n")
end
local score = {}
for i = 1, t do
  score[i] = 0
end
local mma, mfl = math.max, math.floor
for i = 1, n do
  local c, v = cs[i], vs[i]
  local curc, curv = 0, 0
  local csum, vsum = {}, {}
  while 0 < v do
    curc = curc + c
    curv = curv + v
    table.insert(csum, curc)
    table.insert(vsum, curv)
    v = mfl(v / 2)
  end
  for j = t, 1, -1 do
    for k = 1, #csum do
      if j + csum[k] <= t then
        score[j + csum[k]] = mma(score[j + csum[k]], score[j] + vsum[k])
      end
    end
  end
  for k = 1, #csum do
    if csum[k] <= t then
      score[csum[k]] = mma(score[csum[k]], vsum[k])
    end
  end
end
local ret = 0
for i = 1, t do
  ret = mma(ret, score[i])
end
print(ret)