p00019 Factorial
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
```python
num = int(input())
ans = num
for i in range(1, num):
    ans = ans *i

print(ans)

```