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(input())
def f(n):
    if n == 0 : return 1
    else : return f(n - 1) * n
print(f(n))
