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
def main():
    n = int(input())
    for x in range(1, n):
        n *= x
    print(n)


if __name__ == "__main__":
    main()