You're climbing a staircase with n steps. Each time you can climb or steps. How many distinct ways can you reach the top?
With n = 2:
- Way 1: 1 step + 1 step.
- Way 2: 2 steps.
- Answer: .
With n = 3:
- 1+1+1, 1+2, 2+1.
- Answer: .
With n = 4:
- From step 2, take 2 steps → ways to reach step 2.
- From step 3, take 1 step → ways to reach step 3.
- Total: .
Constraints: .