Five pirates are marooned on an island and spend the day collecting coconuts, intending to divide them up the next morning. One of the pirates decides to get more than his share. So, he gets up at night and finding that the coconuts they had collected do not divide by five unless one coconut is removed. So he gives one coconut to a monkey, removes 1/5 of the remaining hides them. Each pirate does this in turn, giving one to the monkey and hiding 1/5 of the rest. When they wake up, everyone notices the diminished pile but since they all stole, no one says anything. So, they give one to the monkey and take 1/5 th of the rest each. What is the least number of coconuts for which this is possible?
Solution is here