Okay, so I have no idea if this is actually the proper method, but it appears to sometimes work (it's not like math is an exact science right/s)
We know e, d and c. Compute f (e - (2 * d + 1)).
If you take d + k where k is an a from (f, 1) you will find a * n. However, it doesn't always lie on (f, 1, 1). It can be further out.
I'm not sure if it helps.