The BIG O Notation

Question

Hi to all.

Attached with this topic there is a file "program.cs" which is a C-Sharp file created with visual studio.
This file contains a simple console application in which the user is asked to enter 3 integer numbers (to be 3 sides of a triangle), and the application outputs if the 3 sides of the triangle given are equilateral, isosceles, scalene triangle or otherwise it outputs that the sides do not make up a triangle.

My problem is that i am asked to examine the complexity of the code which i created using the BIG O notation. 

Can anyone please help me out with this problem?
I am a dummy in this type of notation so please if anyone is going to explain be simple.

Thanks & Regards.
Combinu

P.S. I have also posted this topic in the C-Sharp Language forum so i kindly request a moderator to remove one of the topics, thanks and sorry for any inconvenience caused.