小明刻苦学习英语，终有小成。一日上街，不慎与一老外相撞，连忙说：I am sorry.

　　老外应道：I am sorry too.

　　小明听后又道：I am sorry three.

　　老外不解，问：What are you sorry for?

　　小明无奈，回答说：I am sorry five.