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?
**Example 1:**
```
Input: n = 2
Output: 2
Explanation: 1+1 or 2
```
**Example 2:**
```
Input: n = 3
Output: 3
Explanation: 1+1+1, 1+2, or 2+1
```