let isPrime n =
    let limit = n |> float |> sqrt |> ceil |> int
    let rec check i =
        if i > limit then true elif n % i = 0 then false else check (i+1)
    if n > 2 then check 2 else 2 = n

let n = stdin.ReadLine().Trim() |> int

let result = seq { for n in 2 .. n do n } |> Seq.filter isPrime |> Seq.sum

printfn "%d" result