def caesar(s, k, decode = False):
	if decode: k = 26 - k
	return .join([chr((ord(i) - 65 + k)% 26 + 65)
				for i in s.upper()
				if ord(i) >= 65 and ord(i) <= 90 ])

msg = 
print msg
enc = caesar(msg, 11)
print enc
print caesar(enc, 11, decode = True)