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
n = int(raw_input())

def fact(n):
    if n == 1 or n == 0:
        return 1
    else:
        return n*fact(n-1)

print fact(n)