Consider, we are only allowed to use loops ($while$), addition ($+$), substraction ($-$) and checking if a value is $> 0$. How can one find out, if a certain variable $x$ equals a value $y$? E.g. how can I find out if $x=4$ by only using the aforementioned methods? For $x=0$ I came up with the following:
y = 1 while x > 0: y = y - 1 x = x - 1 while y > 0: do something
This way, $something$ gets only executed if $x=0$. But I have no clue about values above $0$.