During the closing ceremony of the 2013 Southeast Asian Games, the SEAGF Flag was formally handed over from Myanmar to Singapore. This was followed by a song and dance section highlighting Singapore as the next venue. On 27 June 2014, a series of festivities were held at the Singapore Sports Hub, including a fireworks display, to mark the one year countdown to the games. The Sports Hub Community Open House was held in conjunction with the launch to introduce the new sports facilities to the general public. The countdown to the games began on 15 February 2014 with a launch party at the Gardens by the Bay, where the logo, theme and mascot were also introduced. 800 Nanyang Polytechnic students organised a major countdown event on 11 April 2015 to mark the final 50 days in a few days, where about 4,000 people turned up to attend a concert and a sports carnival. On 16 April 2015, the 50-day countdown began with various organisations stacking a number each through a video tribute. This included: Nanyang Polytechnic and Ang Mo Kio residents and Changkat Primary School , London School of Business and Finance Singapore , Compassvale Primary School , Development Bank of Singapore , National Kidney Foundation , CWT Limited , SportCares , Park View Primary School , Sport Singapore  and 41st Battalion Singapore Armoured Regiment . Other organisations were:
Question: How many schools stacked a number through a video tribute?
Answer: 3