Description

A staircase has $N$ steps. You can climb either 1 step or 2 steps at a time. Write a program to compute the number of distinct ways to reach the top.

Input Format

A single integer $N$, the number of steps.

Output Format

Output the total number of ways.

4

5

Hint

• For $60\%$ of the testdata, $N \leq 50$.
• For $100\%$ of the testdata, $1 \le N \leq 5000$.

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