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 Factorial(n):
    if n <= 1: return 1
    return n*Factorial(n-1)
print(Factorial(int(input())))
