Question 3
Determine all functions $f$ from the set of positive integers into the set of positive integers such that for all $x$ and $y$ there exists a non degenerated triangle with sides of lengths
$$
x, \quad f(y) \quad \text { and } \quad f(y+f(x)-1) .
$$
$$
x, \quad f(y) \quad \text { and } \quad f(y+f(x)-1) .
$$