2. Five students are competing in a 10 km race. It is known that after 5 km, the first was Ace, the second Bojan, the third Vuk, the fourth Goran, and the fifth Dejan, while at the end, the first was Vuk, the second Dejan, the third Ace, the fourth Goran, and the fifth Bojan. How many different rankings were there at least during this race? (Rankings where some students are tied are not considered, and it is assumed that two overtakes do not occur at the same time.)
2. The number of different arrangements is equal to the number of pairs of students who have swapped places in the meantime, increased by 1 (due to the first observed arrangement). Since Vuk must overtake Aca and Bojan, Dejan must overtake Aca, Bojan, and Goran, and Goran must overtake Bojan, the number of different arrangements is at least 7. If the overtaking occurs in the order mentioned in the previous sentence, the number of different arrangements will be equal to 7, which is the desired solution to the problem.