Y by Adventure10, Mango247
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
).











