#821. Recursion: factorial
You get n. Find n! with a recursive function.
### Input
n (0 ≤ n ≤ 20).
### Output
Answer.
Examples
Input
4
Output
24
Input
1
Output
1
💡 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.