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

lineNumber = 0

#for line in ["3", "6", "9", "7", "5"]:
for line in sys.stdin.readlines():
    lineNumber += 1

    # get data
    List = map(int, line.strip().split(" "))

    n = List[0]
    ans = 1
    for i in xrange(2, n+1): ans *= i
    print ans