silk road castings
Source: SRMC 2013 P4
September 2, 2018
combinatorics
Problem Statement
In the film there is roles. For each (), the role of number can play a person, and one person can play only one role. Every day a casting is held, in which participate people for roles, and from each role only one person. Let be a prime number such that . Prove that you can have castings such that if we take any people who are tried in different roles, they together participated in some casting ( is a natural number not exceeding ).