Suppose that on a parabola with vertex \(V\) and a focus \(F\) there exists a point \(A\) such that \(AF=20\) and \(AV=21\). Find the sum of all possible values of the length \(FV\). The original answer is in \(\frac{k}{m}\) format, please give the value of k + m.

Let's think step by step and output the final answer within \boxed{}.
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