#!/usr/bin/python
import string
import sys

class cifra_cesar(object):
	alfabeto = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k",
	"l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "1", "2", "3", "4", "5", "6", "7", "8", "9", "0"]
	
	def __init__(self):
		self.menu()

	def menu(self):
		while(1):
			print "1. Criptografar\n2. Descriptografar\n3. Sair\n: \r"
			try:
				opcao = int(raw_input())
				if opcao > 3:
					continue
				elif opcao == 3:
					break
					return
				break
			except:
				continue

		print "Digite o texto: " 
		texto = string.lower(raw_input())
		while(1):
			print "Digite o k: "
			try:			
				k = int(raw_input())
				break
			except:
				continue
		if opcao == 1:
			print self.crypt_descrypt("c", texto, k)
		elif opcao == 2:
			print self.crypt_descrypt("d", texto, k)


	def crypt_descrypt(self, opcao, texto, k):	
		nova_frase = ""
		for letra in texto:
			j = 0	
			for carac in self.alfabeto:
				j += 1
				if letra == " ":
					nova_frase += " "
					break
				elif letra == carac:
					if opcao == "c":
						posicao = j+k-1
						while(1):
							if posicao >= self.alfabeto.__len__():
								posicao = posicao - int(self.alfabeto.__len__())
							else:
								break
						nova_frase += str(self.alfabeto[posicao])
					else:
						posicao = j-k-1
						while(1):
							if posicao >= self.alfabeto.__len__():
								posicao = posicao + int(self.alfabeto.__len__())
							else:
								break
						nova_frase += str(self.alfabeto[posicao])
					break
				elif carac == self.alfabeto[int(self.alfabeto.__len__()) -1]:
					nova_frase += letra
		return nova_frase[::-1]

def main():
	c = cifra_cesar()
	exit

if __name__ == "__main__":
	main()