#907. Stairs: 1-2 steps
A staircase has n steps. Each time you can climb 1 to 2 steps. How many ways are there to reach the top?
### Input
One integer n (1 ≤ n ≤ 50).
### Output
A number.
Examples
Input
37
Output
39088169
Input
39
Output
102334155
💡 You can solve it with Python, JavaScript or blocks. Read the input line by line with input(). Don't print a question (like input("Number: ")). Print exactly what the output asks for, nothing more.