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 fact(n):
  if n == 0 or n == 1:
    return 1
  else:
    return n * fact(n - 1)


print(fact(int(input())))