There are many students in PHT School. One day, the headmaster whose name is PigHeader wanted all students stand in a line. He prescribed that girl can not be in single. In other words, either no girl in the queue or more than one girl stands side by side. The case n=4 (n is the number of children) is like
FFFF, FFFM, MFFF, FFMM, MFFM, MMFF, MMMM
Here F stands for a girl and M stands for a boy. The total number of queue satisfied the headmaster’s needs is 7. Can you make a program to find the total number of queue with n children?

There are multiple cases in this problem and ended by the EOF. 
In each case, there is only one integer n means the number of children (1<=n<=79)

For each test case, there is only one integer means the number of queue satisfied the headmaster’s needs.

算法 递归