Climbing Stairs

Easy 1-D Dynamic Programming
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You can climb 1 or 2 steps at a time. Given n steps, how many distinct ways can you reach the top?

Input: a single integer n.
Output: the number of ways.

Examples

Input: 5 Output: 8

Constraints

1 <= n <= 45

Sample test cases

Input
2
Expected output
2
Input
5
Expected output
8

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