Cast sqrt to int

[meysamhit]

Converting the output of Math.Sqrt to int type, instead of double type, increase performance without changing the algorithm, as a C++ example.

[ali77gh]

Thanks for your PR.
it's may looks like just a cast but its much more and i know it.

[meysamhit]

Yep, sometimes small things make a huge disaster.
An example: https://www-users.cse.umn.edu/~arnold/disasters/patriot.html
It happened just by comparing double values with ==