open System
open System.Text
open System.Text.RegularExpressions
open Microsoft.FSharp.Reflection

[<EntryPoint>]
let main argv =
    let n = Console.ReadLine() |> int
    let ar = Console.ReadLine().Split([|' '|], StringSplitOptions.RemoveEmptyEntries) |> Array.map int
    let counts = Array.zeroCreate 101
    ar |> Array.iter (fun s -> (counts.[s] <- counts.[s] + 1))
    let result = counts |> Array.reduce (fun s x -> s + x / 2)
    printf "%d" result
    0