You are climbing a staircase. It takes n steps to reach the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

Examples

Example 1

Input:  n = 2
Output: 2

There are two ways to climb to the top. 1. 1 step + 1 step 2. 2 steps

Example 2

Input:  n = 3
Output: 3

There are three ways to climb to the top. 1. 1 step + 1 step + 1 step 2. 1 step + 2 steps 3. 2 steps + 1 step

Constraints

• 1 <= n <= 45