let () =
    let rec gcd a b = if b = 0 then a else gcd b (a mod b) in
    let lcm a b = let g = gcd a b in a / g * b in
    let calc a c d =
        let divisible_by_c = a / c in
        let divisible_by_d = a / d in
        let divisible_by_c_and_d = a / lcm c d in
        a - divisible_by_c - divisible_by_d + divisible_by_c_and_d
    in
    let main () =
        let a, b, c, d = Scanf.sscanf (read_line ()) "%d %d %d %d" (fun a b c d -> a, b, c, d) in
        let s = calc b c d - calc (a - 1) c d in
        Printf.printf "%d\n" s
    in
    main ()