open System
open System.Text

let addCommma (args:StringBuilder) =
  let amari = args.Length % 3
  for i in [args.Length-1..-1..0] do
    if i <> 0 && i % 3 = amari
    then args.Insert( i , ',' ) |> ignore
    
  args.ToString()    
  
Console.ReadLine()
|> StringBuilder
|> addCommma
|> printfn "%s"