431. Stairs to Heaven

0

Easy

Arjun is preparing to ascend the celestial staircase. The staircase has N steps leading to heaven. Arjun can choose to climb either one step or two steps at a time. Determine the number of unique ways in which Arjun can reach heaven.

Input Format

The first line of input consists of an integer N, representing the number of steps in the staircase.

Output Format

Print the number of distinct ways in which Arjun can climb to heaven.

Example

Input

3

Output

3

Constraints

1 <= n <= 45
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