There is no way to remove negation in front of

. This is a general fact. Every atom in a formula occurs either in a positive or in a negative position. A position is called positive if it is under even number of negations; otherwise it is called negative. Also, since

is equivalent to

, a premise of an implication is also considered as being under negation. So, for example, the only occurrence of

in the original formula is positive because it is in a premise and under one negation.

Now, whether an occurrence is positive or negative is invariant in equivalent formulas. Since

occurs positively in the original formula, it occurs negatively in the negation, and it will continue to occur in a negative position in any equivalent formula.

What I am saying is that the original formula does not make sense as written because two different things are denoted by the same letter. I think that it is a typo.