# Unable to construct Context-free Grammar from Pushdown Automaton

I have a problem in constructing a Context-free Grammar for the Language $$L = \{a^mb^n : m≠n,m>0,n>0\} .$$ Though I can able to construct a Pushdown Automata.

I can construct a CFG, but it accepts both $m \neq n$ and $m=n$. My CFG is:

$S \to aS/Sb/aSb/aab/abb$.

I cannot able to consturct the CFG to accept for $m \neq n$ alone.

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S ::= aSb | A | B