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 fac(n):
    ans=1
    for i in range(n+1):
        if i is not 0:
            ans*=i
    return ans
n = eval(input())
print(fac(n))
