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(raw_input())
sum= 1
for num in range(1,n+1):
    sum = sum * num
print sum
