万一

Bさん：「I saw the craziest video on YouTube. This golfer made a hole-in-one shot on a par 5 hole! 万一！」
Zさん："I don't know about the term 万一。Literally one out of ten thousand. That is not that rare."
Aさん：「I agree. English is a little better with the phrase "One in a million", but still not great.」
Bさん：「Guys... you are missing the point...」
Zさん："I think a better phrase would be 億一。"
Aさん：「Or even better 兆一。」
Bさん：「If you ask me, the chances you guys will be pedantic in conversation are 一一。」