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

import sys


def fact(n):
    if n == 1:
        return 1
    else:
        return n * fact(n-1)


#input_file = open(sys.argv[1], "r")

#for line in input_file:
for line in sys.stdin:
    n = int(line)
    print fact(n)