A person has between 0 and 300,000 hairs on their head. The urban area of Marseille contains 2,000,000 inhabitants. How many Marseillais have the same number of hairs at a minimum?
Here, we need to apply the generalized pigeonhole principle. The socks are the Marseillais, and the possible number of hairs are the drawers. There are 300001 drawers for 2000000 Marseillais. By the generalized pigeonhole principle, $300001 \times 6 + 199994 = 2000000$, so there are at least 7 people who have the same number of hairs.