To get the first integer after, you can use

`Math.Ceiling`

.To get the first integer before, you can use

`Math.Floor`

.Then the complete formula should be :

C#

`Math.Floor(Math.Sqrt(last)) - Math.Ceiling(Math.Sqrt(first)) + 1`

+1 because if the first integer before last is the first integer after first, the difference will be 0 but you have 1 integer.

For example : with sqrt(first) = 2.3 and sqrt(last) = 3.2

you have 1 integer between the two numbers = 3 but Floor(3.2)=3 and Ceiling(2.3)=3

and Floor(3.2)-Ceiling(2.3) = 0.

This code is written using C#, but I'm sure you can found the

`floor`

and `ceiling`

functions in other language.
Have you tried searching on google for something related to this?