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 math
# print(math.factorial(int(input())))


def f(a):
    if a == 1:
        return a
    return a * f(a - 1)


print(f(int(input())))
