Maya is a bee that likes to help her friends. Willy is a drone bee and Maya’s best friend. He has just discovered that he has no father, and he is worried about that. Maya knows that female bees have two par- ents (one father and one mother), but male or drone bees have a mother but no father. This is because if an egg is laid by an unmated female, it hatches a drone bee, but if, instead, an egg was fertilized by a male, it hatches a female. After Maya talks with Willy about this, he begins to think about the number of ances- tors that he has. He has one mother. He also has two grandparents (one grandmother and one grandfather). And he has three great- grandparents. Since Willy is very lazy, he doesn’t want to perform more calculations and he is asking you to write a program that, given a number of generation, determines how many of Willy’s ancestors belong to that generation, under the assumption that the ancestors at each level are unrelated. Input Your program receives a sequence of positive integers, one per line, each representing the generation. The maximum value for the generation is 80. The input terminates with a ‘0’. Output For each input case, your program must print the corresponding number of ancestors that Willy has in such generation. Sample Input 1 2 3 0 Sample Output 1 2 3