# =================== Echo Function ==========================
class Echo
  def Function__Echo__PlainText(plainText)
    print("Plaintext is [ #{plainText} ] \n")
  end

  def Function__Echo__RandomKey(key)
    print("RandomKey is [ #{key} ] \n")
  end

  def Function__Echo__Field(flist)
    print("Field list is #{flist} \n")
  end

  def Function__Echo__CipherText(cipherText)
    print("Ciphertext is #{cipherText} \n")
  end

  def Function__Echo__Field_LEN(fieldlen)
    print("Field Length is #{fieldlen} \n")
  end

  def Function__Echo__DecryptText(decrypt)
    print("DecryptText is #{decrypt} \n")
  end
end
# =================== Main Function ==========================
class CEA < Echo
  attr_accessor :STRING__plaintext
  attr_accessor :STRING__ciphertext
  attr_accessor :INT__random_cea_key
  attr_accessor :STRING__decrypt_plaintext
  attr_accessor :INT__plaintext_LEN
  attr_accessor :FieldList
  attr_accessor :INT__FieldList_LEN
  def initialize
    @STRING__plaintext         = ""
    @STRING__ciphertext        = ""
    @INT__random_cea_key       = 0
    @STRING__decrypt_plaintext = ""
    @FieldList                 = []
    @INT__FieldList_LEN        = 0
  end
  #[Func 1]--------------------------------------------------------
  def Function__FieldList_SETTING
    (97..122).each do |encoding| #a, b, c, d, ..., z
      @FieldList.push(encoding.chr)
    end
    (65..90).each do |encoding| #A, B, C, D, ..., Z
      @FieldList.push(encoding.chr)
    end
    ('가'..'힣').each do |hangul|
      @FieldList.push(hangul)
    end
    @FieldList.push(" ")
    @FieldList = @FieldList.shuffle
    @INT__FieldList_LEN = @FieldList.length
  end
  #[Func 2]--------------------------------------------------------
  def Function__Random_Secret_Key
    @INT__random_cea_key = Random.new
    @INT__random_cea_key = rand(1...@INT__FieldList_LEN) # 1, 2, 3, 4, ...,25
  end
  #[Func 3]--------------------------------------------------------
  def Function__Encrypt
    @STRING__plaintext.each_char do |plainT_CHAR|
      if (@FieldList.include?(plainT_CHAR))
        position = @FieldList.index(plainT_CHAR)
        position = (position + @INT__random_cea_key)%@INT__FieldList_LEN
        @STRING__ciphertext = @STRING__ciphertext + @FieldList[position]
      else
        @STRING__ciphertext = @STRING__ciphertext + plainT_CHAR
      end
    end
  end
  #[Func 3]--------------------------------------------------------
  def Function__Decrypt
    @STRING__ciphertext.each_char do |ciphterT_CHAR|
      if (@FieldList.include?(ciphterT_CHAR))
        position = @FieldList.index(ciphterT_CHAR)
        position = (position - @INT__random_cea_key)%@INT__FieldList_LEN
        @STRING__decrypt_plaintext = @STRING__decrypt_plaintext + @FieldList[position]
      else
        @STRING__decrypt_plaintext = @STRING__decrypt_plaintext + ciphterT_CHAR
      end
    end
  end
end

#===================== << MAIN >> ===========================
def main
  cea = CEA.new
  cea.Function__FieldList_SETTING
  cea.Function__Echo__Field(cea.FieldList)
  cea.Function__Echo__Field_LEN(cea.INT__FieldList_LEN)
  cea.STRING__plaintext = gets.chomp.to_s
  cea.Function__Random_Secret_Key
  cea.Function__Echo__PlainText(cea.STRING__plaintext)
  cea.Function__Echo__RandomKey(cea.INT__random_cea_key)
  cea.Function__Encrypt
  cea.Function__Echo__CipherText(cea.STRING__ciphertext)
  cea.Function__Decrypt
  cea.Function__Echo__DecryptText(cea.STRING__decrypt_plaintext)
end
main