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It was precision problem, now I got AC

It was precision problem...

I have a huge code for this problem, but I'm still getting WA :cry: I have tested my code with all i/o I could find. So, how can I determine if the output is the distance between the two points? I think my mystake is in this part... I'm doing this:

And... what is the equation to find the points of ...

I have a huge code for this problem, but I'm still getting WA :cry: I have tested my code with all i/o I could find. So, how can I determine if the output is the distance between the two points? I think my mystake is in this part... I'm doing this:

And... what is the equation to find the points of ...

Can anyone give me some ideas to solve this problem? Is this a graph problem, or geometric? Please help.