Ok, thank you.
Should I consider the problem as resolved, or come here in half a year and try to change it once again?

One more question... It's my first kata, I would like to know how to make it interesting.
I noticed that even though the problem is interesting, it's hard to present it in interesting way. Plenty of text, many parameters are the biggest issue here - at least I think so. I though that for people who like algorhitms it's a nice task, but it seems I was wrong.

Could you give me a tip, the idea, how would you create a task about epidemic and exponential growth?

As there is no reply and I think it's clear now what to do if multiplier is not integer, I'm marking issue as resolved.

I added a performance check. Let me know if it's a good idea, as numbers there are not realistic. On the other hand we may want to find parameters for the disaease and to do this we'll be running the model thousands of times. Maybe it's better to use possible values and just loop it?

Changed to: "In case multiplier is a fraction, round the result numbers only." Is it acceptable?

You definitely shoudn't round each day, although I can understand why you consider it.
Generaly speaking for every single value here we take a mean for thousands of people. Doing it by looking at individuals we should look like this:

• Incubation time: 2-14 days
• Infecting time: 1-20 days
  Ofc we need to take these numbers randomly, set up weight. That's why it's better to simplify.

Anyway, there is an information that results must be rounded. Should I add any additional information?

Thank you for pointing it out. I changed the definition of multiplier and missed it in that comment. Fixed.

Just use round() function returning the results. How can I make it clearer?

Apparently the bug was stupid and doesn't affect other parts, so I published it again. Added a note.

1. Migrants != immigrants. Correct me if I'm wrong. It's not only foreign people, because for example in Poland most of infected people who arrived were Poles who spent winter break in Italy.

2. I changed "migrants" to "infected migrants", that's what I meant.

3. Everything here is an average. Incubation for COVID-19 can last from 2 to 14 days. People will infect shorter or longer. The beauty of this is that if we don't care about individuals, we can take some constant values and make the model much simpler.

4. "any people can infect any other people in the whole country". Yes, again to simplify things. The model still works for the very beggining of epidemic, like first 2 months. As I understand, you want to add SIR model together with containers (infection spreads faster in a container than between them). It's nice and something to think about, together with giving the number of confirmed cases and estimating infected people with incubating virus and more random values. My point was to make this task "as simple as possible" while still talking about incubation time and infecting time.

5. "active: you're considering that the contagioon is possible only for already sick people". Again, to simplify things. Actually it's something I could mention, but I'm not sure where... There are people who are not sick and they're spreading virus. In case of COVID-19 it's around 10%, who will never get sick and they are a huge problem if we try to just isolate people, without making tests.

6. Changed infecting time and recovery time description. Recovery time will be overlaping anyway, just the question is should it overlap the incubation time. I left it as it was.

7. About death rate, we can bother, but 10% while 90% of them are over 60 years old... This part is actually too realistic and I think it's the main reason why many governments didn't want to introduce heavy restrictions straight away. They don't bother.

8. Dogs are unrealistic, it's just a joke with some truth. Noone cares about animals during epidemic. To this day numbers are very small thanks to restrictions and high higiene standards, but if milions of people will be dying, then noone will talk about animals.

9. Anya description changed.

10. The most important one! I clearly made a mistake in script (I can't count to 5). I'll dig deeper to check other values. I don't know why it happened yet, so I'm unpublishing the task.

Thank you for wall of text, very useful :)

I wrote it from the beggining. I guess that means that new errors appear, but hopefully it'll be better this time.

The text is long, with a lot of data, what makes it boring and hard to read. I allowed myself to add some epidemic humor. Please let me know if it's not appropiate or delete/unpublish if I may get banned for it.

For government and statistics people are not important. The focus is on growth (in case of epidemic exponential growth) :)
Jokes aside, I'll change it.

"Finally, you never give a concrete section explaining either what the inputs look like, or what the actual output look like." I understood it as giving input and output. Can you explain it?

I need an hour or two without thinking about it, so I'll lose this description in my mind and I'll be able to create something new. Thank you for your contribution!

To get first batch of data you only need incubation time and infection rate.
Once again, can you take a look please?

You're right. There are a lot of terms which should be defined better. As there are many informations, I decided to introduce them step by step. I'm thinking about creating a summary or introduction, just listing those terms. Is it a good idea? Any more suggestion?

I rearanged it a bit, can you take a look?

Publishing it yesterday was a big mistake, I rushed it. I am sorry for that. I improved description, changed some definitions so it's easier to undestand them. If you have any doubts or result is wrong (I could make a mistake as well), please let me know.