def first_letters_freq(last_names)
  letters = Hash.new(0)
  last_names.sort.each do |name|
    letters[name[0].chr] += 1
  end

  return letters
end

@last_names = ['Amberg', 'Levchuk', 'Azazel', 'Arbuzov', 'Letov']

require 'erb'
template = ERB.new <<-EOF
  <div>
  <% 
    frequencies = first_letters_freq(@last_names)
  %>
  </div>
EOF