Slovakia

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Novak Djokovic of Serbia celebrates after defeating Lukas Lacko of Slovakia in their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 13, 2014..(AP Photo/Aaron Favila)

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Novak Djokovic of Serbia celebrates after defeating Lukas Lacko of Slovakia in their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 13, 2014..(AP Photo/Aaron Favila)

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Novak Djokovic of Serbia makes a forehand return to Lukas Lacko of Slovakia during their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 13, 2014.(AP Photo/Eugene Hoshiko)

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Former Grand Slam champion Boris Becker of Germany looks down onto Rod Laver Arena as he prepares to watch defending champion Novak Djokovic in his match against Slovakia's Lukas Lacko at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 13, 2014.(AP Photo/Eugene Hoshiko)

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Defending champion Novak Djokovic of Serbia waves as he walks onto Rod Laver Arena to play Lukas Lacko of Slovakia in their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 13, 2014.(AP Photo/Eugene Hoshiko)

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Novak Djokovic of Serbia chases down a ball for a return to Lukas Lacko of Slovakia during the first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 13, 2014.(AP Photo/Eugene Hoshiko)