open System

let separateStr (arg:string) =
  let rec splitStr  (acc) (argStr:string) = 
    match argStr.Length with
    | 0 | 1 | 2 | 3 -> argStr + acc
    | _ -> argStr.Substring(0, argStr.Length-3)
           |> splitStr  ("," +  argStr.Substring(argStr.Length-3) + acc) 
  splitStr "" arg
  
Console.ReadLine() 
|> separateStr  
|> printfn "%s"