Task: Question Answering
Input (English): Context_1 : Daniel Mark Nestor {'1': ", '2': ", '3': ", '4': "} (Serbian Cyrillic: Данијел Несторовић; born September 4, 1972 as Danijel Nestorović) is a Canadian professional tennis player. He is one of the foremost doubles players in tennis history due to his longevity and continued success at the top of the men's game. s of 2016 , he is 11th for most men's ATP titles in Open Era history. In January 2016, Nestor became the first doubles player in ATP history to win 1000 matches. Context_2 : Grant Stafford and Kevin Ullyett were the defending champions. Stafford chose not to participate this year. Ullyett partnered with Piet Norval but lost in the semifinals to the eventual champions Justin Gimelstob and Sébastien Lareau. <BR>Justin Gimelstob and Sébastien Lareau won in the final over David Adams and John-Laffnie de Jager, 7–5, 7–6. Context_3 : David Adams and Marius Barnard were the defending champions but they competed with different partners that year, Adams with Olivier Delaître and Barnard with Piet Norval. Context_4 : Daniel Nestor and Nenad Zimonjić were the defending champions, but they split in 2011. Daniel Nestor qualified with his new partner Max Mirnyi and Nenad Zimonjić with Michaël Llodra. Context_5 : Pieter ("Piet") Norval (born 7 April 1970) is a former tennis player from South Africa, who turned professional in 1988. The right-hander represented his native country in the doubles competition at the 1992 Summer Olympics in Barcelona, where he partnered Wayne Ferreira. The pair won the silver medal, after losing the final to Boris Becker and Michael Stich from Germany. Norval reached his highest singles ATP-ranking on 19 June 1989, when he became the no. 125 of the world. Context_6 : Tomás Carbonell and Donald Johnson were the defending champions, but did not participate together this year. Carbonell partnered Juan Balcells, losing in the first round. Johnson partnered Piet Norval and successfully defended his title. Context_7 : Piet Norval and Kevin Ullyett were the defending champions, but did not participate this year. Context_8 : Katarina Srebotnik and Piet Norval were the defending champions, but lost in second round to Kim Clijsters and Lleyton Hewitt. Context_9 : Mike Bauer and Piet Norval were the defending champions, but did not participate this year. Context_10 : Lucas Arnold and Tomás Carbonell were the defending champions, but did not participate together this year. Arnold partnered Martín García, losing in the first round. Carbonell partnered Piet Norval, losing in the first round. fact_1 : Daniel Mark Nestor {'1': ", '2': ", '3': ", '4': "} (Serbian Cyrillic: Данијел Несторовић; born September 4, 1972 as Danijel Nestorović) is a Canadian professional tennis player. fact_2 :  He is one of the foremost doubles players in tennis history due to his longevity and continued success at the top of the men's game. fact_3 : Pieter ("Piet") Norval (born 7 April 1970) is a former tennis player from South Africa, who turned professional in 1988. fact_4 :  The pair won the silver medal, after losing the final to Boris Becker and Michael Stich from Germany. Question: Who has won more medals, Daniel Nestor or Piet Norval?
Output (English): Pieter Piet Norval