open System

let S = Console.ReadLine()
let strCharCount s c = s |> Seq.filter(fun s -> s = c) |> Seq.length
let charCounts = strCharCount S
let treCounts = "tre" |> Seq.map charCounts
let zip = Seq.zip treCounts [|1;1;2|] 
let div = zip |> Seq.map( fun (a, b) -> a / b ) |> Seq.min

printfn "%d" div