open System
open System.Collections.Generic

[<AutoOpen>]
module Cin =
    let read f = stdin.ReadLine() |> f
    let reada f = stdin.ReadLine().Split() |> Array.map f

    let readInts() =
        read string
        |> Seq.toArray
        |> Array.map (fun x -> Convert.ToInt32(x.ToString()))

module Util =
    let strRev s =
        s
        |> Seq.rev
        |> Seq.map string
        |> String.concat ""

[<EntryPoint>]
let main _ =
    let N = read int
    let P = reada int64

    let mutable k = Array.fold (fun acc (x: int64) -> acc * Numerics.BigInteger(x)) 1I P
    while k > 9I do
        let mutable a = k
        let mutable dsum = 0I
        while a > 0I do
            dsum <- dsum + (a % 10I)
            a <- a / 10I
        k <- dsum

    printfn "%A" k
    0 // return an integer exit code
    0 // return an integer exit code