which championship were in the category, grand slam?
australian open, french open, wimbledon, us open
of these, which dates did they occur?
14 january 2014- 27 january 2014, 25 may 2014- 8 june 2014, 23 june 2014- 6 july 2014, 25 august 2014- 8 september 2014
of these, which championship was the latest date?
us open