open System.Text.RegularExpressions
let ``No.345 最小チワワ問題``() =
  
  let s = stdin.ReadLine()

  let regCWW = Regex("(c[abdefghijklmnopqrstuvxyz]*w[abcdefghijklmnopqrstuvxyz]*w)")

  let regCWW = Regex("(c[abdefghijklmnopqrstuvxyz]*w[abdefghijklmnopqrstuvxyz]*w)")

  
 
  match regCWW.IsMatch s with
  | false -> -1 |> stdout.WriteLine
  | true  -> 
    seq { for g in regCWW.Matches(s).[0].Groups do yield g.Value.Length }
    |> Seq.minBy (fun s -> s)
    |> stdout.WriteLine

``No.345 最小チワワ問題``()