Fibonacci army
Description
King Cambyses loves Fibonacci numbers. He has several armies. Today he wants to make a new army for himself and he wants the number of men in this army to be the n-th Fibonacci number.
Given n you should find n-th Fibonacci number. The set of Fibonacci numbers start with f0 = f1 = 1 and for each i ≥ 2, fi = fi - 1 + fi - 2.
Input contains a single integer n (1 ≤ n ≤ 20).
Write a single integer. The n-th Fibonacci number.
Input
Input contains a single integer n (1 ≤ n ≤ 20).
Output
Write a single integer. The n-th Fibonacci number.
Samples
2
2
1
1