Each participating country, other than the host country, may submit suggested problems to a Problem Selection Committee provided by the host country, which reduces the submitted problems to a shortlist. The team leaders arrive at the IMO a few days in advance of the contestants and form the IMO Jury which is responsible for all the formal decisions relating to the contest, starting with selecting the six problems from the shortlist. The Jury aims to order the problems so that the order in increasing difficulty is Q1, Q4, Q2, Q5, Q3 and Q6, where the First day problems Q1, Q2, and Q3 are in increasing difficulty, and the Second day problems Q4, Q5, Q6 are in increasing difficulty. The Team Leaders of all countries are given the problems in advance of the contestants, and thus, are kept strictly separated and observed.