class Kumiawase

  @@checked_list = {}

  def initialize(start_list)
    start_list = start_list.dup
    start_list.delete(nil)
    sorted_list = start_list.sort
    @list = start_list.map do |i|
      sorted_list.index(i)
    end
  end

  def check
    if @@checked_list.include?(@list)
      return @@checked_list[@list]
    end

    @list.size.times do |s|
      nokori_list = @list.dup
      chukan_list = []

      i = s
      nokori_list.delete(i)
      j = 0
      nokori_list.delete(j)

      chukan_list[j] = i

      while true
        j = @list[j]
        nokori_list.delete(j)
        if chukan_list.include?(j)
          if chukan_list[i] == j
            flag = true
          else
            flag = false
          end
          break
        else
          chukan_list[i] = j
        end

        i = @list[i]
        nokori_list.delete(i)
        if chukan_list.include?(i)
          if chukan_list[j] == i
            flag = true
          else
            flag = false
          end
          break
        else
          chukan_list[j] = i
        end
      end

      if flag
        if nokori_list.empty?
          @@checked_list[@list] = true
          return true
        else
          if Kumiawase.new(nokori_list).check
            @@checked_list[@list] = true
            return true
          end
        end
      end
    end

    @@checked_list[@list] = false
    return false
  end
end

gets
a = gets.split.map{|s|s.to_i-1}

kumi = Kumiawase.new(a)
if kumi.check
  puts "Yes"
else
  puts "No"
end