German scientists think that your 36 keeps working while you are asleep.To show that they were 37 ,they gave two groups of people a problem to work out.One group went to sleep and the other group stayed 38 . The result? The people who slept worked out the answer more quickly,suggesting that their brains had been trying to 39 the answer while the people were asleep.So,make sure you get enough sleep tonight, 40 you’ll be at your best tomorrow.