// Learn more about F# at http://fsharp.org

open System

let isPrime n =
    if n = 1L then
        false
    else
        seq { 2L .. n }
        |> Seq.filter (fun i -> i * i <= n)
        |> Seq.forall (fun i -> n % i <> 0L)

[<EntryPoint>]
let main argv =
    let n = stdin.ReadLine() |> int

    let primes =
        Seq.initInfinite (fun i -> i |> int64)
        |> Seq.skip 100000
        |> Seq.filter isPrime
        |> Seq.take 10

    let niceNumbers =
        seq { 1L }
        |> Seq.append
            ((Seq.zip primes primes) |> Seq.map (fun (p, q) -> p * q))
        |> Seq.sort

    niceNumbers
    |> Seq.item (n - 1)
    |> printfn "%d"
    0 // return an integer exit code