Five sailors are skipped on a desert island . The spend all day collecting coconuts which they put into a large pile. When they are asleep one awakes and decides to take his share i.e., one fifth. Unfortunately there is monkey watching so he tosses one to the monkey and then finds the pile divides evenly for his fifth. he takes his share and hides it. Each sailor then does exactly the same (including one to the monkey). What is the minimum number of coconuts needed so this can be done?