Passage: Lou Yun (simplified Chinese: 楼云; traditional Chinese: 樓雲; pinyin: Lóu Yún; born June 23, 1964 in Hangzhou, Zhejiang) is a retired Chinese gymnast who competed in the 1984 and 1988 Summer Olympic Games, winning the vault twice.

Question: How many times did the gymnast Los Yun win the vaults?
twice