Lewis and Lilly are playing a game with a coin. The coin is going to be tossed times. After a toss, Lewis will give Lilly if the toss is heads, and Lilly will give Lewis if it is tails. As long as Lewis and Lilly both have at least , they will toss again. If one of them has a balance of , then the game ends. If they both start out with , what is the probability that they break even? That is, what is the probability that both finish the game with ?