The lowest pairs are the mismatched nines, eights, sevens, and fives. World Rugby also organises the quadrennial Rugby World Cup Sevens. Fiji's national sport is Rugby Sevens. The Olympic form of rugby is known as Rugby Sevens. Discard the sevens of clubs and spades. There are variations for under-19 and Sevens rugby. Carlsberg has also sponsored the Hong Kong Rugby Sevens in 2015. Llangoed hosts an annual rugby sevens contest. Rugby is increasing in popularity, especially with the annual Safari Sevens tournament. The Luzhniki Stadium also hosted the 2013 Rugby World Cup Sevens. Serevi started 2001 by leading Fiji in the 2001 Rugby World Cup Sevens in Argentina. In 2009, Dubai hosted the 2009 Rugby World Cup Sevens. The USA Sevens, a major international rugby event, was held there from 2007 through 2009. Nauru competed in the 2015 Oceania Sevens Championship in New Zealand. Scotland were champions of the 2016 London Sevens.