I am sorry five!

[xiaolu]

D君刚学了点儿外语(英语)，某天在街上，一不小心踩了一老外的脚，D君急忙说：“I'm sorry,” 老外也礼貌的答：“I'm sorry, too.” D君一听，急忙说了句：“I'm sorry three.” 老外一听傻了：“What are you sorry for?” D君又很无奈的答：“I'm sorry five.”