Mr. Yi went to Mr. Gong's house as a guest. When he arrived at the door, he didn't know which floor Mr. Gong lived on
he asked a grandma and several children who were sitting in the shade at the door. Xiao Li said: Mr. Gong doesn't live on the first floor.  Xiaomei said: Mr. Gong doesn't live on the second floor.  Xiaofang said: Mr. Gong doesn't live on the third floor.  Xiaohong said: Mr. Gong doesn't live on the fourth floor. Xiaoyu said, :This building has only four floors and he live in the open-air. At this time, the old woman smiled and said to Mr. Yi: These children are really naughty, but most of them are telling the truth, only one person lies.
Mr. Gong lives on the fourth floor