def main
  s_ar = STDIN.gets.chomp.split('').sort

  if s_ar.uniq.length == 1
      puts "No"
      return
  end

  s_ar.each_slice(2) do |a|
    if a[0] != a[1]
      puts "No"
      return
    end
  end
  puts "Yes"
end

main