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
# -*- coding:utf-8 -*-

def main():
    n=int(input())
    count=n
    a=1

    while count!=1:
        a*=count
        count-=1

    print(a)
        
if __name__ == '__main__':
    main()