There are X number of dots on a sheet of paper. All of the dots are connected by one-way arrows. Each dot has exactly ten arrows pointing toward it and ten arrows pointing away from it. No pair of dots is connected by more than one arrow.

If we can reach from any dot to any of the other dots using a maximum of two arrows, find the minimum value of X required.

The Prize for This Question: Rubik’s Revolution 3” Cube With LED and Voice/Sound Effects

Send your answer to **ieee@bilkent.edu.tr** by** 5:30 p.m.** on **November 11**, or visit **ieee.bilkent. edu.tr/zeka** to submit your answer online, and get a chance to win the prize!

This question was prepared by Emrehan Halıcı, president of the Turkey Intelligence Foundation, for Bilkent IEEE.