Even if you didn't "make it nice", you should still be able to get it out. The key bit is deciding "there must be a way of differentiating my series from (i) to get something that looks like (ii)". Which is somewhat of a "STEP-ism". That is, if you were just given a series looking like (ii), there's no guarantee differentiating will actually give you something nice. But because it's STEP, you can be a lot more confident that it will actually work.