let ``No.279 木の数え上げ``() =

  stdin.ReadLine()
  |> Seq.filter (fun id -> (id = 't' || id = 'r' || id = 'e'))
  |> Seq.countBy (fun id -> id)
  |> Seq.minBy (fun (id , n) -> 
    match id with
    | 't' -> n
    | 'r' -> n
    | 'e' -> (n / 2)
    |  _  -> 0   
    )
  |> fun (id, n) ->
    match id with
    | 't' -> n
    | 'r' -> n
    | 'e' -> n/2
    | _   -> 0
    |> stdout.WriteLine

``No.279 木の数え上げ``()