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


if __name__ == '__main__':
    factorial = 1
    n = int(input())
    for i in range(1, n+1):
        factorial *= i
    print(factorial)