Little Elephant and Cards

Little Elephant from the Zoo of Lviv likes cards. He has N cards, each of which has one of 1000 colors. The colors are numbered from 1 to 1000. Little Elephant and Big Hippo are playing the following game. At first Little Elephant takes some subset of cards, and Big Hippo takes the rest of them. Here, Little Elephant can choose to take all of the cards, or none of the cards. Then they play 1000