If you want to paste code directly into your question, you should then select it and use the 101/010 button to indent it so that it is displayed properly. But it’s better to just have a link and explain how your code works.
You might like to try out a testcase of n=21, to see how your program responds to a big result. Ideally you should have tried out n=100, the limit value, before submitting.
The expected result for 21 is 51090942171709440000. Factorial 100 has 158 digits.
You used to have some code that was relatively close to a solution for very small integers, but I suspect you have been making random changes. That might explain why you appear to have a double output of result.