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
import sys

def kai(n):
  if(n <= 1):
    return 1
  else:
    return n*kai(n-1)

for n in sys.stdin:
  print kai(int(n))