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
        if S.[x] = 't' then 
            t <- t + 1
        else if S.[x] =  'r' then
            r <- r + 1
        else if S.[x] = 'e' then
            e <- e + 1
    done
    e <- e / 2
    let res = min (min t r) e
    
    printfn "%d" res
        
    0