I have two related questions on the representability of integers 
by quadratic forms in two variables :

  (1) Let $f: {\mathbb Z} \times {\mathbb Z} \to {\mathbb Z}  $ be such a quadratic
form, i.e. we have $f(x,y)=ax^2+bxy+cy^2+dx+ey+g$ for some integer constants
$a,b,c,d,e,g$. Suppose that $f$ is not surjective, i.e. some integer is not represented
by $f$. Is it true that there is an integer constant $C$ such that in any block of
$C$ consecutive integers, at least one of them is not represented by $f$ ?


 (2) If the answer to (1) is yes, is there a uniform bound ? In other words,
is there a uniform constant $C$ such that for any non-surjective $f$, in any block of
$C$ consecutive integers, at least one of them is not represented by $f$ ?