open System

let solve (n: string) =
  let f = n.Substring(0, 1)
  let e = n.Substring(1)
  let ea = e.ToCharArray()
  let el = ea |> Array.length
  let edl = ea |> Array.distinct |> Array.length

  if f = "1" && edl = 1 then el
  elif f = "1" && edl = 0 then 1
  else -1

let N = Console.ReadLine()

solve N
|> Console.WriteLine