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 cal(x):
    sum = 1

    for i in range(x):
        sum *= i+1

    return sum

if __name__ == "__main__":
    a = int(raw_input())
    print cal(a)