#! ruby
# yukicoder My Practice
# author: Leonardone @ NEETSDKASU

N = gets.to_i

items = {}

powerup = 0

N.times do
    abc = gets.chomp.split
    abc.each do |x|
        if items.include? x
            powerup += 1
            items.delete x
        else
            items[x] = 1
        end
    end
end

powerup += items.keys.size.div(4)

puts powerup