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
#import math
ans= int(1)
for i in range(2,int(input())+1):
    ans*=i
print(ans)