Background

Special for beginners, ^_^

Eating Chocolates

Problem Description

Mingming's mother came back from a business trip and brought him a beautiful box of delicious chocolates ($N$ chocolates in total, $0 < N < 20$). She told Mingming he could eat one or two chocolates each day. Assuming Mingming eats chocolate every day, in how many different ways can he finish all the chocolates?

For example:

• If $N = 1$, Mingming eats it on the $1$st day, so there is $1$ way;
• If $N = 2$, Mingming can eat $1$ on day $1$ and $1$ on day $2$, or eat $2$ on day $1$, so there are $2$ ways;
• If $N = 3$, Mingming can eat $1$ on day $1$ leaving $2$, or eat $2$ on day $1$ leaving $1$, so he has $2 + 1 = 3$ ways in total;
• If $N = 4$, Mingming can eat $1$ on day $1$ leaving $3$, or eat $2$ on day $1$ leaving $2$, so there are $3 + 2 = 5$ ways in total.

Now given $N$, write a program to compute the number of ways Mingming can eat the chocolates.

Input Format

One line: the integer $N$.

Output Format

One line: the number of ways Mingming can eat the chocolates.

Sample Input

4

Sample Output

5

Constraints

1s, 1024KiB for each test case.