Problem:
Factorial

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.

Sample Input

5

Output for the Sample Input

120

Solution in Python (judge verdict: Accepted)

n = int(raw_input())
ans = 1
for i in range(1, n+1):
	ans = ans * i
print ans