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 fac(n):
    f = 1
    for i in range(2, n + 1):
        f *= i

    return f

n = int(input())
print(fac(n))