题目描述

Fibonacci sequence, also known as the Golden Section sequence, is introduced by mathematician Leonardo Fibonacci taking rabbit reproduction as an example, so it is also called "rabbit sequence". It refers to such a sequence:
1, 1, 2, 3, 5, 8, 13, 21, 34,... Mathematically, Fibonacci sequence is defined recursively as follows: F (1) = 1, F (2) = 1, F (3) = 2, F (n) = F (n-1) +F (n-2) (n >= 4, n
Now you are required to write a program to figure out the N number of the Fibonacci sequence.

输入格式

N stands for the following table of the Fourier series.

输出格式

The number n of the case of the Fourier series.

20
3

6765
2