You are climbing a staircase. It takes n steps to reach the top.
Each time you can either climb 1 or 2 steps. Return the number of distinct ways you can climb to the top.
Example 1:
Input: n = 2
Output: 2
Explanation: There are two ways to climb to the top: 1 + 1 and 2.
Example 2:
Input: n = 3
Output: 3
Explanation: There are three ways to climb to the top: 1 + 1 + 1, 1 + 2, and 2 + 1.
Example 3:
Input: n = 5
Output: 8
Explanation: The 8 distinct ways include combinations like 1+1+1+1+1, 2+1+1+1, 1+2+2, etc.
1 <= n <= 45