import sys

def run(text, shift):
  text = text.lower()
  ord_of_a = ord('a')
  result = ''
  for letter in text:
      if letter in 'qwertyuiopasdfghjklzxcvbnm':
        letter = chr(abs((ord(letter) - ord_of_a + shift) % 26 + ord_of_a))
      result += letter
  return result

def test_a_to_b():
   actual = run('a', 1)
   expected = 'b'
   if actual != expected:
     print 'Test a to b fail!'

def test_z_to_a():
   actual = run('z', 1)
   expected = 'a'
   if actual != expected:
     print 'Test z to a fail!'

def test_leaves_spaces():
   actual = run('Hello World', 1)
   expected = 'Ifmmp Xpsme'
   if actual != expected:
     print 'Test leaves spaces fail!'

def test_decrypt():
   actual = run('ifmmp xpsme', -1)
   expected = 'hello world'
   if actual != expected:
     print 'Test decrypt fail!'

if __name__=='__main__':
  test_a_to_b()
  test_z_to_a()
  test_leaves_spaces()
  test_decrypt()
  op = sys.argv[1].lower()
  text = sys.argv[2]
  shift = int(sys.argv[3])
  if op == 'd':
      shift = -shift
  print run(text, shift)