Hello all, I have come across an incredibly difficult riddle which I would like to share with you: 100 people are assigned with natural numbers between 1 and 100. These numbers are entirely random and independent of one another, meaning there can be duplicates (and consequently missing numbers). Each person receives an anonymous list of 99 numbers representing everyone else's numbers but not her own. She then makes a guess regarding her own number based on the numbers she sees and the strategy that was agreed upon in advance by the group. They cannot communicate in any way and cannot hear what others have guessed, i.e. they are completely isolated all the way through. The strategy they develop should guarantee that at least 1 person makes a correct guess regardless of the given numbers. I have battled through this brain crushing puzzle, and would be glad to see your ideas and thoughts. Cheers! Btw, I am sorry if this riddle was already posted, I tried searching before posting.