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 mutable result = 0
for i in 2 .. n do
    if isPrime i then result <- result + i
printfn "%d" result