Sultan and sages
Source: Moscow mathematic olympiad 2022, P11.6
September 29, 2022
combinatorics
Problem Statement
The Sultan gathered court sages and offered them a test. There are caps of different colors, known in advance to the sages. The Sultan said that one of these caps will be put on each of the sages, and if for each color
write the number of caps worn, then all numbers will be different. Every sage can see the caps of the other sages, but not own cap. Then all the sages will simultaneously announce the supposed color of their cap.
Can sages advance agree to act in such a way that at least of them are guaranteed to name a color
right?