open System
open System.Text

let min (x:int) (y:int) =
    
    if x < y then
        x
    else 
        y
  
[<EntryPoint>]
let main args =    
    let S:string = Console.ReadLine()
    let mutable t, r, e = 0, 0, 0
    for x = 0 to S.Length-1 do
            match S.[x] with
            | 't' -> t <- t + 1
            | 'r' -> r <- r + 1
            | 'e' -> e <- e + 1
    done
    e <- e / 2
    let res = min t r
    
    printfn "%d" res
        
    0