let ``No.51 やる気の問題`` () =
    let W = int <| stdin.ReadLine()
    let D = int <| stdin.ReadLine()
    seq [ D..(-1)..1 ]
    |> Seq.take (D-1)
    |> Seq.fold (fun s n -> s - (s/(n*n))) W
    |> printfn "%d"
``No.51 やる気の問題`` ()