"""
 cipher.py
 A quick version of cryptographic stuff we did a few weeks ago.
 (This is the "docstring", or interface spec :
  what is this, and how do I use it?)
 Jim M, Sep 30, GPL
"""

# (This is an implementation comment: what are the 'how' details?)
# I decided to use mod arithmetic 
# to implement the encoding and decoding.
#

def main():
  print "-- cipher ---\n"
  key = int(raw_input("What is the key? (13) "))
  word = raw_input("What is the word? (cat) ")
  new_word = ""
  for char in word:
    crypt_char = chr(((ord(char) - ord('a') + key) % 26) + ord('a'))
    new_word = new_word + crypt_char
  print "'%s' encrypted is '%s' \n" % (word, new_word)

main()