Scanf.scanf "%d" (fun n ->
    let arr = Array.init (n + 1) (fun i -> if i < 2 then 0 else i) in
    let rec loop_i i =
        let rec loop_j j =
            if j > n then loop_i (i + 1) else ( arr.(j) <- 0; loop_j (j + i))
        in
        if i * i < n then loop_j (i * i)
    in
    loop_i 2;
    Array.fold_left (+) 0 arr |> Printf.printf "%d\n"
)