This question has been vote-closed because there is a C# version and it's "off topic".
The question asks for an F# solution (after some editing; it was originally posted poorly), and a comment by "Won't" on this (Meta) very question says it's not valid to ask F# questions because you can convert F# to C#.
Despite being the same framework, F# is not C#. F# is functional (not purely, but still, it exists separately from C# for a reason). It has features like Pattern Matching that C# does not, and this feature was even used in the answer of this question.
To me, this looks like a completely valid question, and it's already been re-opened once.
Can someone please clarify the rules around not being able to have solutions in a different language that is "a bit like" an existing answer in another language or why this question does not give an understanding of the problem and/or code? It has exactly as much information in it as the C# version, which is apparently considered fine.