defmodule Main do
  def input, do: IO.read(:line) |> String.trim
  def ii, do: input() |> String.to_integer
  def li, do: input() |> String.split |> Enum.map(&String.to_integer/1)
  def yn(b), do: IO.puts(if b, do: "Yes", else: "No")

  def main do
    ss = IO.binread(:eof) |> String.split("\n", trim: true)

    Enum.at(ss, 1)
    |> String.split
    |> Enum.map(&String.to_integer/1)
    |> Enum.frequencies
    |> Enum.map(fn {_, v} -> div(v, 2) end)
    |> Enum.sum
    |> IO.puts
  end
end