alphabet = "abcdefghijklmnopqrstuvwxyz"

def substitute(text, plain, cipher):
    result = ""
    for ch in text:
        if ch in plain:
            result += cipher[plain.find(ch)]
        else:
            result += ch
    return result

#cdfghijklmnopqstuvwxyzebra
#abcdefghijklmnopqrstuvwxyz
def make_phrase(phrase):
	result = alphabet
	for ch in phrase:
		result = result.replace(ch, "")
	return phrase + result

cipher = make_phrase("zebra")
phrase = "we are the knights who say ni!"

print(phrase)
ciphertext = substitute(phrase, alphabet, cipher)
print(ciphertext)
plaintext = substitute(ciphertext, cipher, alphabet)
print(plaintext)