[Python] How to end while loop when same value is inputted twice?

How can I write a while loop that asks for a user for input, and breaks when the same value is used twice in a row?

This is my current attempt, which tries to use len(set(word)) to get the previous word:

story = ""

while True:
word = input("Give me a word: ")
if word == "end" or word == len(set(word)):
break
story += word + " "

print(story)

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