The first of the International Mathematical Olympiads (IMOs) was held in Romania in 1959. The oldest of the International Science Olympiads, the IMO has since been held annually, except in 1980. That year, it was cancelled due to internal strife in Mongolia. Because the competition was initially founded for Eastern European countries participating in the Warsaw Pact, under the influence of the Eastern Bloc, the earlier IMOs were hosted only in Eastern European countries, gradually spreading to other nations. Sources differ about the cities hosting some of the early IMOs and the exact dates when they took place. The number of participating countries has risen from 7 at the inaugural event to 14 in 1969, 50 in 1989, and 104 in 2009. North Korea is the only country to have been caught cheating, resulting in its disqualification at the 32nd IMO in 1991 and the 51st IMO in 2010. In January 2011, Google gave €1 million to the IMO organization to help cover the costs of the events in 2011–2015. (Full list...)