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MONTE-CARLO, MONACO - APRIL 12: Detail shot of the shoes of Roger Federer of Switzerland during his second round match against Guillermo Garcia-Lopez of Spain during day three of the Monte Carlo Rolex Masters at Monte-Carlo Sporting Club on April 12, 2016 in Monte-Carlo, Monaco. (Photo by Michael Steele/Getty Images)

MONTE-CARLO, MONACO - APRIL 12:  Detail shot of the shoes of Roger Federer of Switzerland during his second round match against Guillermo Garcia-Lopez of Spain during day three of the Monte Carlo Rolex Masters at Monte-Carlo Sporting Club on April 12, 2016 in Monte-Carlo, Monaco.  (Photo by Michael Steele/Getty Images)