You are right! Thank you

by that time i didn't know about sprintf)

Right now you are using logical OR to check if no requirement is violated
If you were to check if the requirements were met instead ( <= turns into >, >= turns into < etc)
and use logical AND to chain the checks, it would be a tiny bit more efficient.
If any of the requirements are not met, the rest of the expression does not need to be evaluated
as one false in a chain of ANDs will always equal false.

In this example the impact is negligeble but it is best practice to fail fast.

strcat spam is what happens when you don't know about sprintf