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 kj(n):
    if n==0 or n==1:return 1
    return n*kj(n-1)
print(kj(int(input())))

