• Organisers pledge to learn from Brazil’s hosting of 2014 World Cup• Countdown to Rio 2016 begins as tickets go on sale• Tessa Jowell: Why I can’t wait for the Olympic GamesRio de Janeiro is on track to deliver a “fit, clean and fun” Olympic Games on time and on budget, according to the deputy chief executive of the city’s organising committee.Speaking at Rio 2016 headquarters before Monday’s release of tickets for the Games, Leonardo Gryner also said his organisation had learned lessons from Brazil’s hosting of the 2014 Fifa World Cup, an event which attracted widespread protests.