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
#!/usr/bin/python


def datasets():
    s = raw_input().strip()
    yield int(s)
    
def main():
    for n in datasets():
        print reduce(lambda a, b: a*b, range(1, n+1))
        
if __name__ == '__main__':
    main()