There was a girl who wanted chocolate, but she lacked 10 coins to buy, and there was a boy who also wanted chocolate, but he lacked only 1 coin to buy. Then they decided to collect all the money together and buy one chocolate, but they still lacked 1 coin.
How much does chocolate cost?
Yyy: So what, the girl didn’t have a single coin?
ZZZ : Oh yeah This is always the case when a boy and a girl want to buy chocolate together.