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
def fac(x):
    if x<=1: return 1
    return fac(x-1)*x

while True:
    try:
        n=input()
        print fac(n)
    except EOFError: break