Factorial
Multiply 1 through N together to compute N factorial.
Input format
One line with an integer N (0 to 20).
Output format
Print N factorial, the product 1 * 2 * ... * N. By definition 0! is 1.
Constraints
- Values fit in a 64-bit signed integer
- Trailing whitespace and a trailing newline are ignored by the judge
Read from stdin, write to stdout. Sample cases below show the exact format.
Sample cases
Example 1
Input
5Expected output
120Example 2
Input
0Expected output
1