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
n = int(input())

def fact(n):
   ans = 1
   for n in range(n,1,-1):
      ans *= n
   return ans

print(fact(n))
