Hi Yaj,
I hope my remark is not too silly (because unfortunately I am not a mathematician): Are you sure that your equation has a solution anyway? The general form is:
$f(q) = \int f(p) K(q,p)\mbox{d}p$
and this is true for
$K(q,p) = \delta(p-q)$, but in your case
$K$ is not the Dirac-Deltafunction ...
Henrik