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
from math import *
PI = 3.1415926535898
while True:
	try:
		n = input()
		ans = 1
		for i in range(1, n+1):
			ans *= i
		print ans
	except EOFError:
		break