Rio Olympics 2016 officially gets under way with the opening ceremony on Friday – but the action kicks off two days before that with the football. The first group games in the women's tournament take place today – so-called day minus 2 – with Sweden facing South Africa.The men start tomorrow, when Iraq play Denmark. Football matches start early at the Olympics simply for scheduling reasons, as it was at London 2012.With 16 men's and 12 women's teams, there are 58 matches to get through, with only six rest days.