You are climbing a stair case. It takes n steps to reach to the top. Each time you can either climb **1 **or **2** steps. Write a program to **count the number of ways**, the person can reach the top.

** Problem Note **

- Given n will be a positive integer.

**Example 1 **

```
Input: n = 1
Output: 1
Explanation: There is only one way to climb to the top
```

**Example 2 **

```
Input: n = 2
Output: 2
Explanation: There are two ways to climb to the top:
(1, 1) and (2)
```

**Example 3**

```
Input: n = 4
Output: 5
Explanation: There are five ways to climb to the top:
(1, 1, 1, 1), (1, 1, 2), (2, 1, 1), (1, 2, 1) and (2, 2)
```