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