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 Factorial(N):
    if N == 0 :
        return 1
    else :
       return Factorial(N-1)*N

def main():
    n = int(input())
    print(Factorial(n))

if __name__ == '__main__':
    main()

