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
# Factorial
def f(n):
    if n == 1: return 1
    return f(n-1) * n
n = int(input())
print(f(n))
