123. The sum time limit per test: 0.25 sec.
The Fibonacci sequence of numbers is known: F_{1} = 1; F_{2} = 1; F_{n+1} = F_{n} + F_{n1}, for n>1. You have to find S  the sum of the first K Fibonacci numbers.
Input First line contains natural number K (0<K<41).
Output First line should contain number S.
Sample Input 5
Sample Output 12  

Name 
