type Scanner() = class
    let mutable hold = [||]
    let mutable index = 0
    member public this.Next() =
        if hold.Length > index
        then 
            index <- index + 1
            hold.[index - 1]
        else
            let mutable st = stdin.ReadLine()
            while st = "" do st <- stdin.ReadLine()
            hold <- st.Split(' ')
            if hold.Length = 0
            then
                this.Next()
            else
                index <- 1
                hold.[index - 1]
            
    member public this.NextI32() =
        this.Next() |> int

    member public this.ArrayI32(n: int) =
        [for _ in 0 .. n - 1 -> this.NextI32()]

    member public this.NextI64() =
        this.Next() |> int64
    
    member public this.ArrayI64(n: int) =
        [for _ in 0 .. n - 1 -> this.NextI64()]

    member public this.NextF32() =
        this.Next() |> float32
    
    member public this.ArrayF32(n: int) =
        [for _ in 0 .. n - 1 -> this.NextF32()]

    member public this.NextF64() =
        this.Next() |> double
    
    member public this.ArrayF64(n: int) =
        [for _ in 0 .. n - 1 -> this.NextF64()]
end

[<EntryPoint>]
let main args =
    let rec atoz flg list = 
        flg |> function 
        | true -> list |> function
            | head :: _ when head = 'A' -> List.rev list |> atoz false
            | _ :: tail -> atoz true tail
            | [] -> 0
        | false -> list |> function
            | head :: _ when head = 'Z' -> list.Length
            | _ :: tail -> atoz false tail
            | [] -> 0
    let s = Scanner().Next() |> Seq.toList
    
    atoz true s |> printfn "%i"
    0
