open System
type Sol() =
    member this.Solve() = 
        let S = stdin.ReadLine()
        
        let ts = Seq.fold (fun s c -> s + (if c = 't' then 1 else 0) ) 0 S
        let rs = Seq.fold (fun s c -> s + (if c = 'r' then 1 else 0) ) 0 S
        let es = Seq.fold (fun s c -> s + (if c = 'e' then 1 else 0) ) 0 S
        
        printfn "%d" (Seq.min (ts::rs::(es/2)::[]) )
        
let mySol = new Sol()
mySol.Solve()