Write a program which reads an integer n and prints the factorial of n. You can assume that n ≤ 20.



Input

An integer n (1 ≤ n ≤ 20) in a line.

Output

Print the factorial of n in a line.

Example

Input

5


Output

120
#!/usr/bin/python

def main():
	input = raw_input()

	n = int(input)
	print int(factorial(n))

def factorial(n):
	if (n <= 1):
		return 1

	return n * factorial(n - 1)

main()