One day, the chief of the dwarves decided he wanted to test his tribe. So that night, he told the dwarves that he would paint on each dwarf's back a dot colored either red or blue. Each dwarf will know everyone else's dot color, but not their own.
Every dwarf with a red dot on his or her back is to go to the dining hall on the Nth day, where N is the number of dwarves with a red dot on their backs. The presence of any blue-dotted dwarves at the dining hall on the Nth day constitutes a failure.
Furthermore, after the dwarves get their backs painted, they are not allowed to communicate using any means, including (but not limited to) speaking, punching, and holding mirrors. No dwarf is allowed to know what color he is until after the trial is over.
The dwarves can meet on the day before the trial in order to talk strategy. What strategy should they use?
EDIT: Note the question linked in the comments here is not quite the same as this problem. The blue-eyes problem is more of a induction-based problem, while the dwarf problem is a simple strategy-based problem.
In the blue-eyes problem, the main point is who leaves the island and when, whereas in this problem, the main point is how to create a strategy involving no communication in order to fulfill a specific condition.