local args = {...}

local handle,content = fs.open(args[1],"r"),false
content = handle.readAll()
handle.close()

local chars = {}

for match in content:gmatch(".") do
  if(not chars[match]) then
    chars[match] = 1
  else
    chars[match] = chars[match]+1
  end
end

local sorted = {}

for k,v in pairs(chars) do
  if(not sorted[v]) then
    sorted[v] = {k}
  else
    table.insert(sorted[v],k)
  end
end

handle = fs.open("output","w")
handle.write(textutils.serialize(sorted))
handle.close()